• Sryan Bruen

A history of December cold spells

Updated: Nov 29, 2021

Following on from the November cold spells blog post, I decided to do a December version of this due to popularity. Before getting onto the nit and gritty details of this post, I need to reiterate the introduction of the previous one, particularly if people did not read it.

Severe cold or snowy weather is unusual at any time of year in the UK & Ireland due to the geography of our location where we reside near the North Atlantic Ocean, a large body mass of water with a prevalent westerly flow (frequently referred to as "zonal") bringing mild air from off the ocean. This is especially the case in early winter when the North Atlantic jet stream is at its peak in strength on average due to the steep temperature gradient between the relatively mild tropics and the severely cold North Pole. The continent also tends to slowly cool down from the summer season and easterly flows in December tend to not be as cold as they would be later in the season like say February. December is the least snowy of the three meteorological winter months for this reason and many even have March as a snowier month on average.

Severe cold weather conditions in the UK & Ireland during the month of December have occurred time and time again. Everybody talks about the often touted "December to Remember" of 2010 as it was extraordinarily cold and so recent (which will be discussed later) but what other years were there? Find out below.

1878 - Severe Victorian era winter off to a flying start

The Victorian era was renown for some severely cold winters in its time during the 19th century and 1878-79 was one of the coldest and most brutal of the lot. The infamous snowy winter of 1947 is said to be the snowiest since 1878-79.

November 1878 had already been a very cold month and nature was about to level up to 100 on the cold scale through December. A cold front spread south on the 7th December and introduced a very cold north to northeasterly flow that manifested itself and stuck around for 2 weeks up to Boxing Day. It only got more and more severe coming up to Christmas as the snow continued to fall from constant snow showers in the unstable northeasterly flow and due to the slack nature of the airflow, there was also plenty of severe frosts with minus double digits not uncommon.

The Central England Temperature (CET) for December 1878 was only -0.3°C and is the joint 4th coldest on record in the CET series. January 1879 was also severely cold with a CET of -0.7°C. This would be the last time there would be two consecutive subzero CET monthly means until "The Daddy" of 1962-63. Who knew that this winter would be the start of a prolonged unusually cold year in 1879 (the last year with a CET in the 7s)?

Some reports from December 1878:

- Camborne (Cornwall); Heavy thunderstorm with snow (12th)

- Coston Rectory (Norfolk); Hoar frost, trees with an inch of rime on branches (13th)

- Sunderland (Durham); 17" of snow (9th)

- Llandovery (Carmarthenshire); The hardest frost set in that we have had for 18 years, the snow fell to a depth of 3ft (7th)

- Boston (Lincolnshire); Ponds and drains were frozen sufficiently to bear skaters on the 10th. On the 25th, the river Witham was frozen from Boston to Lincoln.

- Monkstown (Dublin); Much snow on 8th, 9th, 10th, 11th and 22nd. Skating continued from 5th to 26th.

Christmas 1878 was the coldest Christmas on record. Gainford (Durham) got down to -18.3°C which remains the lowest temperature on Christmas Day in the UK to present. The daily CET for Christmas Day 1878 was -5.8°C whilst the CET minimum for the day was -11.2°C! There was only one day with a colder CET minimum than that in December 2010. Edenfel (Co. Tyrone) got down to -17.8°C on Christmas morning, the Northern Ireland record low for December until 2010.

At the long-term Irish station Phoenix Park (Co. Dublin), with temperature records since 1855, December 1878 was the second coldest month on record behind only January 1881 which occurred 2 years and 1 month later! It was also only the second time that Phoenix Park has recorded a monthly mean temperature below freezing with December 2010 and February 1895 just missing. Markree Castle (Co. Sligo) got down to -14.8°C on December 17th and 25th.

NCEP 500mb height reanalysis for 7th December 1878 showing a cold front has cleared the UK & Ireland with a cold northeasterly flow following on behind.

NCEP 500mb height reanalysis for 17th December 1878 showing a severe cold and wintry northerly flow over the UK & Ireland.

1879 - One year on...

As I mentioned in the 1878 section above, the year of 1879 was a crazy cold one and December 1879 would be yet another well below average month temperature wise. In fact, it was the 14th consecutive month colder than average and wouldn't be the last as January 1880 was also very cold. The CET for December 1879 was 0.7°C so not quite as cold as 1878 but still a bitter one and the first half of the month in particular was extremely cold.

The month started appropriately with a slack easterly flow over the UK and snow showers but what was most notable was the frost. Blocking collapsed over the UK by the 6th December but it remained cold with frosts of unusual severity. Kelso (Roxburghshire) reported a minimum temperature of -26.7°C on 4th December 1879 which is the second lowest December temperature on record in the UK and would hold as the UK December record low until 1995. There was a disregarded reading of -30.6°C on 3rd December at Blackadder near Kelso due to non-standard instrumentation.

NCEP 500mb height reanalysis for 2nd December 1879 showing a slack easterly flow over the UK & Ireland.

1890 - The coldest December on CET record.

1890 appeared in the November cold spells blog post and it's back again as it was the coldest December on CET record with a monthly mean temperature of -0.8°C which 2010 did not quite beat although away from England, December 2010 was colder than December 1890. Scotland was almost 2°C milder than England & Wales in December 1890. December 1890 was the last time that the December CET was beneath freezing until 2010.

The exceptionally cold end to November 1890 continued into December with frequent easterly winds for much of the month which favoured the coldest weather to be in the south. Whilst it was a cold month in the north, Atlantic air ensured it wasn't as severely cold as further south at times. Ireland had similar fare. In fact this cold spell lasted up to mid to late January 1891 in the south of the country. It was quite a foggy month and exceptionally cloudy in the south as well as cold with Westminster in London observing zero hours of sunshine all month.

Lakes, rivers and canals froze to depths of several inches. The Thames was frozen for over a mile near Twickenham whilst the Dee near Chester was frozen for 5 and a half miles. The maximum temperature at Reading on 14th December 1890 was only -6°C and the place had a continuous spell of 11 ice days in a row, with observing an exceptional 36 through the winter of 1890-91. London recorded 36 consecutive air frosts between 13th December and 12th January 1890-91 whilst Sumburgh (Shetland) had only 4.

12 inches of snow fell at Bridgwater on 18th-20th December whilst 10 inches in Pontypridd Castle, 8 inches in Yeovil, 4 and a half inches in Berkhamsted and 4 inches in Coventry. It wasn't the snowiest December in the world but there was still some snow to be had.

NCEP 500mb height reanalysis for 4th December 1890 showing a ridge of high pressure to north of Scotland drawing in a cold easterly flow to England & Wales.

1906 - A Christmas to Remember

A year generally renown and remembered for its extraordinary heatwave in early September, the Christmas period of 1906 was certainly not one to forget either. Not a particularly cold December overall as compared to those already brought up but it brought a noteworthy Christmas nevertheless which was more dramatic than what the charts suggest.

There was frequent wintry showers in a northwesterly flow coming up to Christmas in 1906. An area of low pressure came down in the flow during Christmas Day with the first snowfalls arriving in Northern Ireland and SW Scotland around lunchtime, reaching Manchester by 8 p.m. Snowfall intensity in this low was heavy and intense with depths of snow in excess of 10cm for many with some reaching as much as 30cm in the space of only a couple of hours. The heaviest band was from Manchester to East Anglia and snow settled in central London just after midnight. Most of the country was white on Boxing Day.

Some reports on the Christmas 1906 snow event:

Camden Square (London): 4.5 inches of snow feel on the night of the 25th December.

Crowborough (East Sussex): Blizzard with 5 inches of snow Christmas night.

Southport (Merseyside): Total depth of snow 9.3 inches

Bolton (Greater Manchester): Fall of snow of 8 inches on 25th, lighter falls on the 26th, 28th, 29th and 30th produced a depth of 18 to 20 inches of undrifted snow.

Haverfordwest (Pembrokeshire): Snowstorm with gale on 26th, depth 10 inches by 29th

Douglas (Isle of Man): Between 1 and 2 inches fell from 25th to 30th.

Dumfries (Dumfries & Galloway): 5 inches of snow on the night of 25th.

Dublin: A period of snow and frost set in on morning of 26th and last the 30th.

There was a tornado reported on Christmas on the Moray Firth.

Minima got down to as low as -13.3°C at Birr Castle (Co. Offaly) and Markree Castle (Co. Sligo) on December 29th whilst -16°C was recorded at Swarraton (Hampshire).

NCEP 500mb height reanalysis showing an unusually snowy northwesterly to northerly flow on Christmas Day 1906.

1920 - From very cold to exceptionally mild.

The winter of 1920-21 was not a cold one and in fact contained one of the mildest Januaries on record (with a CET of 7.3°C) but did contain one significant cold spell through mid-December 1920 with a snow event for wide parts of the south on 11th and 12th December. Clacton in Essex reported an accumulation of 35cm and snow lay for 10 consecutive days in Plymouth before exceptionally mild air took over from the 18th and remained that way for the rest of 1920. Raunds (Northamptonshire) got down to -18.3°C on the 13th and 14th.

One of the less talked about December snow events and cold spells as its significance is less than that of many others but its contrast with what was to follow and how much snow parts of southern and southeastern England had made it standout. Maximum temperatures frequently reached 12-15°C by Christmas Eve 1920.

NCEP 500mb height reanalysis for 12th December 1920 showing a cold easterly flow delivering heavy powdery snow to the UK and Ireland.

1927 - The infamous Christmas blizzard.

December 1927 was quite a cold month with a CET of 2.1°C and very easterly similar to December 1890 but was not nearly as foggy and featured a severe snowstorm for the south of the UK during Christmas into Boxing Day which was one of the worst of the 20th century.

A cold northeasterly brought snow showers to the east coast on Christmas Eve 1927. A low pressure had moved into the English Channel on Christmas Day and this engaged with the cold air with precipitation initially falling as rain but the low pulled down even colder air and the rain turned readily to snow. By midnight, many southern and southeastern counties had snow cover with horrendous conditions on Boxing Day as gale force northeasterly winds led to blizzards and severe drifting. Villages were cut off by drifts up to 20 feet and food supplies had to be air dropped. Transport was virtually paralysed with train services cancelled or seriously delayed. Depths of snow were approaching 10 inches in central London.

The snow cover from the snowstorm was to last until the New Year but this would end in more disaster with severe flooding from snow melt and high tides associated with southerly gales on 7th January 1928, particularly on the Thames. 14 casualties were caused by the floods from mostly drowning in basements and many more became homeless.

NCEP 500mb height reanalysis for 25th December 1927 showing low pressure attacking from the south delivering snow to much of England.

1933 - A proper north/south divide.

As compared to 1927, the cold in December 1933 was much less dramatic but the month featured a significant north/south divide in temperature with the north often being mild whilst the south was frosty with freezing fog. This was in some way similar to 1890 but the contrast was much more stark. Scotland was over a degree milder than England & Wales. Lerwick (Shetland) and Stornoway (Outer Hebrides) had only one air frost all month where it was milder than average whilst all days of the month recorded ground frost at Rickmansworth (Hertfordshire) and 30 days at Hampstead (Greater London). The CET for December 1933 was 1.6°C.

It was the 13th driest December on record for England & Wales as stubborn high pressure blocked Atlantic weather fronts and the winter was the 5th driest in a very dry year. The maximum temperature at Manchester on the 6th was only -5°C in freezing fog and many rivers froze over including the Thames in its upper reaches above Oxford.

NCEP 500mb height reanalysis for 6th December 1933 showing high pressure in control and gentle cold southeasterly winds.

1937 - Unusual variety of extremes for December.

December 1937 was relatively cold with a CET of 3.0°C and contained some very interesting weather ranging from blizzards to thundersnow to fog to sleet to hail. The CET for 4th-20th December 1937 was only 1.1°C but the cold weather did not last to Christmas as it became much milder.

Newport (Isle of Wight) recorded 105mm in the 24 hours to 9 a.m. on 8th December and severe flooding was reported here. Meanwhile, Shaftesbury in Dorset reported level snow of 1-2 ft. Durham reported 11 inches of snow on the 11th. Undrifted snow was 18 inches deep at Balmoral (Aberdeenshire) on the 15th whilst even in Ireland there was a good deal of snow with some roads being impassable but snow data here is unknown.

Two trains had collided in a snowstorm in Scotland during this cold spell in December 1937 with 35 unfortunate casualties. Braemar (Aberdeenshire) got down to -21.7°C on the 13th.

NCEP 500mb height reanalysis for 8th December 1937 showing an easterly flow with low pressure around the UK giving heavy rain and snow for some.

1938 - The December beasterly unleashed and a very white Christmas.

Winter 1938-39 preceded a series of freezing cold winters that would come during the early 40s and it was known as a winter of teases with some significant snow events but rarely became very cold for long. One time it did was the pre-Christmas period in December 1938.

Blocking from Russia retrogressed westward toward Scandinavia through mid-December 1938 and ushered in a severely cold easterly coming up to Christmas with tons of snow showers from troughs embedded in the flow. It was a true and rare case of a December beasterly with an airmass unusually severe for that early in the season.

The temperature remained beneath freezing in Lympne (Kent) from 18th to 26th December 1938 (222 hours of frost). Manston (Kent) had 147 hours of frost whilst Ross-on-Wye (Herefordshire) had 111 hours. It did not get above -3°C at Oxford on the 20th which was widely the coldest December day in 30 years since 1908 or 1890. Braemar (Aberdeenshire) got down to -15.6°C on the 22nd whilst Markree Castle (Co. Sligo) got down to -11.1°C at the same time.

Undrifted snow lay to a depth of 1 foot at places as far apart as Bellingham (Northumberland), Oundle (Northamptonshire) and Woburn (Bedfordshire).

Snow was widespread on Christmas morning and it was the snowiest Christmas of the 20th century in terms of locations with snow cover on Christmas morning.

NCEP 500mb height reanalysis for 20th December 1938 showing a severely cold airmass giving plentiful snow showers to the UK and Ireland.

NCEP 850hPa temperature reanalysis for 20th December 1938 showing the beast being unleashed to the UK and Ireland from the east.

1950 - The coldest since 1890 and second coldest of the 20th century.

With a CET of 1.2°C, December 1950 was the coldest December since 1890 and the second coldest of the 20th century behind only 1981.

The month contained a number of snowfalls and formed as part of the snowiest winter of the century in highland Scotland with 102 snow days lying at Dalwhinnie in 1950-51 as compared to 83 days in 1946-47. Snow fell on 22 days at Ushaw (Durham), 20 days at Bwlchgwyn (Clwyd), 19 days at Princetown (Devon) and Glenlivet (Banffshire). Snow was 20 inches deep at Dalwhinnie in the highlands on the 3rd, 10 inches at Cockle Park (Northumberland) on the 4th, 11 inches at Bwlchgwyn (Clwyd) and 10 inches at Houghall (Durham) on the 5th, 10 inches or more at Scarborough (North Yorkshire), Bournemouth (Dorset), Weymouth (Dorset), Poole (Dorset) and the Isle of Wight on the 15th, 14 inches at Scarborough (North Yorkshire) and Lowestoft (Suffolk) on the 16th. Dublin reported a significant covering of snow on the 15th. Safe to say there was plenty of snow!

Dalwhinnie got down to -18.3°C on the 15th. Markree Castle (Co. Sligo) had -11.1°C on the same day.

NCEP 500mb height reanalysis for 15th December 1950 showing an unstable northerly flow.

1961 - The forgotten severe cold New Year of 61/62.

When the cold 60s is mentioned, the exceptionally cold winter of 1962-63 always comes to mind and gets plenty of attention. The preceding winter, 1961-62, wasn't nearly as cold and was in fact relatively close to average overall with a cold December and a severely cold March in the following spring.

The CET for December 1961 was 2.2°C so it was certainly a cold one with the most wintry part of the month being the Christmas to New Year week which was dominated by northeasterly or easterly winds. Before this, there was plenty of frosts and freezing fog to be had. The CET from 18th December to 4th January 1961-62 was -1.7°C and the second half of December 1961 was the coldest second half of December of the century.

There was widespread falls of snow as pressure fell around 29th December. Snow lay 12-16 inches deep in the English Midlands on the 30th and 31st. The frosts were the main noteworthy thing about this spell however. Carlow recorded -14.6°C on 31st December which was the December record low for the Republic of Ireland until 2010 whilst Cannich in the highlands got down to -22.2°C, the lowest December temperature in the UK since 1879. London had its lowest temperature for any month on record on 1st January 1962 following on from the snowfalls with -16.1°C at Northolt.

NCEP 500mb height reanalysis for 30th December 1961 showing cold northeasterly winds and low pressure giving snow to places.

1962 - The coldest winter since 1740 gets underway.

As the third coldest winter on CET record and coldest since 1740 was underway, it began with frosty and foggy conditions in early December 1962 with fears of a repeat of the deadly smog of 10 years prior occurring once again but fortunately it was not on the same scale. It became more unsettled mid-month and changeable.

High pressure over Scandinavia brought a cold easterly flow just before Christmas but the high collapsed quickly and replaced by heights rising over Greenland with a northerly flow for Christmas which gave a white Christmas to parts of Scotland and many had seen the first of many snowfalls to come through Boxing Day when it snowed for many hours. Depths had approached two and a half feet for some.

An area of low pressure pushed into the Bay of Biscay through the final days of December and easterly winds intensified leading to heavy drifting on snow that had already fallen. Conditions were atrocious with proper whiteout scenes widely across the UK and Ireland. Snow lay 12 inch deep for lots of places even in the London area. Casement Aerodrome (Co. Dublin) reported a depth of 45cm of snow on 31st December 1962 which is the highest depth on record at a synoptic Irish station but there was tons of drifting so accurate measurements were difficult to come by without heavy skewing from easterly gales. High tides and strong easterly winds also led to bad coastal flooding on eastern coasts of England and Ireland.

The CET for December 1962 was 1.8°C, coldest since 1950 but this was due to the relatively milder weather mid-month. 23rd December to 3rd January 1962-63 had a CET of -2.4°C whilst 2nd-6th December had -1.1°C.

NCEP 500mb height reanalysis for 30th December 1962 showing bitterly cold easterly gales giving deep drifting snow to many.

1968 - Another year ending in "8" with a white Christmas (Okay couldn't think of another heading, I'm sorry)

Much of December 1968 was of the anticyclonic type but a depression moved southeastwards across Cornwall on Christmas Eve and whilst initially heavy rain at first turned to snow later in the evening over parts of southern England. On Christmas morning, snow lay 10-15cm deep here. Winds were generally north and northwesterly for the next couple days following and more snow occurred where it was heavy in Norfolk, Lincolnshire and the East Riding of Yorkshire where high winds caused deep snow drifts which blocked many roads near the east coast. Whitby reported 6ft snow drifts with a max gust of 92 mph during a blizzard.

Undrifted snow accumulated to a depth of about 40cm at High Mowthorpe (North Yorkshire) and 50cm at East Dereham (Norfolk).

NCEP 500mb height reanalysis for 28th December 1968 showing a very cold and snowy northerly flow for eastern coasts of the UK.

1970 - Oh look another white Christmas.

High pressure set up shop between Scotland and Iceland around Christmas 1970 and this allowed a cold easterly flow to bring snow showers and around freezing maxima to the south of the UK. Snow depths were generally around 20cm over the higher hills of the SE and a few centimetres on lower ground. The CET for 24th December to 5th January 1970-71 was -0.6°C.

Not a very significant cold spell/snow event comparing to those we've discussed but it was the most recent white Christmas for parts of southeast England!

NCEP 500mb height reanalysis for 25th December 1970 showing a cold easterly flow giving some snow showers to southern England.

1978 - The last New Year blizzard

Much of December 1978 was very wet with frequent areas of low pressure coming up against blocking to the north and air was not cold enough for much of this precipitation to turn to snow. However, an easterly airstream began to intensify towards New Year just after Christmas ushering in severe cold air from Scandinavia. Any floodwaters would freeze over quickly and snow showers were to become widespread with easterly winds leading to drifting on New Year's Eve 1978. Much like with 1962, easterly gales made accurate measurements of snow depths difficult with tons of drifting. Drifts were up to about 2 metres on the 31st. Cornwall was hit badly in particular. The CET for 31st December to 6th January 1978-79 was -2.9°C. The CET maximum on 31st December was only -2.4°C, coldest day since January 1963 and coldest December day since 1908.

In Ireland, snow depths reached 26cm at Casement Aerodrome (Co. Dublin), 16cm at Claremorris (Co. Mayo) and 15cm at Cork Airport (Co. Cork). The deep snow cover and light winds allowed for frosts of unusual severity through early January 1979 too including Ireland's lowest temperature since 1881 with -18.8°C at Lullymore (Co. Kildare) on January 2nd.

NCEP 500mb height reanalysis for 31st December 1978 showing a bitterly cold easterly giving drifting snow to England, Ireland and Wales.

1981 - Severe cold and snowy, at times stormy!

December 1981 was the coldest December of the 20th century and the coldest since 1890 as well as reportedly the snowiest since 1878 with numerous snowstorms. It had a CET of only 0.3°C with the most severe weather occurring mid-month as it began and ended mild and benign. Similar in some ways to December 1878.

Cold air pushed southward on the 6th December 1981 and lasted to about the 27th for much of the UK with Ireland and southwestern parts of the UK tending to have more modification from time to time due to Atlantic depressions attacking from the west and southwest trying to dislodge the cold air. At first precipitation fell as rain on the 6th as airmasses became increasingly colder, the rain turned to snow leaving a fairly general snow cover across both countries. On the 11th December, a low tracked close to the English Channel and brought heavy snow to southern parts of England including 26cm at Heathrow.

Clearing skies and a slack flow with deep snow cover resulted in some exceptionally cold nights to follow. Shawbury (Shropshire) got down to -22.6°C early on the 12th December which was already the lowest December temperature in the UK since 1879 but the following night was even colder with -25.1°C early on the 13th at the same place which was an English record low for not only December but any month and the most extraordinary thing of all is that it would be beaten only a month on in January 1982... what a phenomenal pair of months December 1981 and January 1982 really were. Dunsany (Co. Meath) got down to -12.9°C on the 12th which was Ireland's lowest December temperature since 1961.

A deep depression approached from the west on the 13th December and gave blizzards to the Midlands and northern England with extensive flooding on southern coasts from strong winds and high tides. There was a storm surge up the Bristol Channel too. The Queen had to stay the night in a local pub in the Cotswolds as she was stranded in deep drifts of snow. In Ireland, Cork had daily rainfalls greater than 60mm on the 13th and 14th whilst Casement Aerodrome in Dublin recorded a max wind gust of 150 km/h (that's 93 mph in old money) which was a new wind record for Dublin.

Another storm led to the infamous Penlee lifeboat disaster in Cornwall on 19th December where a Penlee lifeboat was capsized and there were 16 casualties unfortunately. There were further snowfalls and sharp frosts coming up to Christmas. Whilst no snow fell on Christmas Day as the country was under a ridge of high pressure, there was widespread snow lying deep across the UK but less so in Ireland. Perthshire reported a snow depth of 47cm on Christmas Day which is the deepest snow measured on Christmas Day in the UK.

NCEP 500mb height reanalysis for 11th December 1981 showing a largely slack flow over the UK with a low near Biscay about to give a snow event to England.

NCEP 500mb height reanalysis for 13th December 1981 showing a large storm depression attacking from the west.

NCEP 500mb height reanalysis for 19th December 1981 showing another storm depression that would lead to the Penlee lifeboat disaster.

1995 - Lowest December temperature on record in the UK.

Well known for its impressive feat of recording the lowest December temperature on record in the UK and joint lowest for any month on record, December 1995 was the coldest since 1981. High pressure over Greenland fed extremely cold Arctic air south to Scotland from the 18th and would lead to a severe final week of 1995 for the north of Ireland and the UK.

Christmas brought a blizzard to Scotland with the Shetland Isles accumulating 35cm of snow on Christmas Day. The temperatures were the main talking point of this cold spell with Altnaharra in the highlands observing 4 consecutive nights with -20°C or less including -27.2°C on the 30th which is the lowest temperature on record for the UK, equal with February 1895 and January 1982. The temperature rose from -21.2°C at midday to -1.0°C under three hours as the wind strengthened at Altnaharra in the afternoon on the 30th. As it continued to increase, the temperature had reached a max of 1.7°C here which made for an exceptional diurnal temperature range of 28.9°C, the greatest UK daily temperature range on record. The maximum temperature at Fyvie Castle (Aberdeenshire) on the 29th was also a record for the UK with -15.9°C, the lowest for any month and would nearly be equalled in December 2010. Letterkenny (Co. Donegal) got down to -13.3°C on the 28th whilst Clones (Co. Monaghan) recorded -11.0°C on the 27th.

NCEP 500mb height reanalysis for 30th December 1995 showing a slack airflow over the far north of Scotland before a deep Atlantic low ended the cold spell.

2000 - Notable white and cold Christmas to New Year week, particularly for the era.

A mostly unsettled and relatively mild month continuing on from the deluge autumn of 2000 but there was a sudden flip to greatly colder conditions during Christmas to New Year week with northerly winds setting in. A series of polar lows and troughs in the flow led to widespread falls of snow, at times heavy. The M40 was closed for a time near Oxford and 20cm was reported at Luton Airport (Bedfordshire). It was a white Christmas for some but not one of the standouts with the main snow events occurring from the 27th to the 29th. A polar low gave 17cm at Knock Airport (Co. Mayo) and 11cm at Mullingar (Co. Westmeath) on the evening of the 27th. A secondary polar low gave a dumping of 5-10cm in the Dublin area on the 28th. There was a thunderstorm reported at Shannon Airport on the same day with blowing snow. A family home at Causeway Village (Co. Kerry) was destroyed by the lightning in one of the thunderstorms.

Straide (Co. Mayo) recorded -14.0°C on the 29th December which was Ireland's second lowest December temperature on record at the time and lowest since 1961 but this would later be destroyed by 2010 a decade later. Ice days conditions were also a feature including only -2.2°C on the 29th at Dublin Airport with freezing fog. Parts of Scotland remained beneath freezing from the 25th to the 31st.

NCEP 500mb height reanalysis for 26th December 2000 showing the UK & Ireland in the grips of a very cold and unstable northerly flow.

2009 - Start of the coldest winter since 1978-79.

The coldest December since 1996 (1995 in Scotland) with a CET of 3.1°C and would form part of what would become the coldest winter since 1978-79. It all began in mid-December 2009 with easterly winds giving snow to southeast England on 17th December followed by a northerly flow by the 20th.

6 inches of snow fell in Stevenage (Hertfordshire) on the 17th. Further snow consistently fell up to Christmas widely with a temporary thaw away from Scotland just after Christmas before northeasterly winds brought the cold back southward by New Year's Eve setting up for a very cold spell during the first half of January 2010. Snow depths generally in the 10-20cm range. Black ice became an increasing concern with up to 40 vehicles crashing on the A35 in Dorset because of black ice.

Braemar (Aberdeenshire) got down to -18.4°C on the 29th, the lowest temperature since March 2001 and lowest for December since 1995. This minimum was then followed by a maximum of -12.2°C on the 30th. Boyle (Co. Roscommon) got down to -12.2°C on Christmas Day.

NCEP 500mb height reanalysis for 17th December 2009 showing a cold easterly flow across the UK & Ireland.

2010 - The December to Remember.

Widely the coldest December on record setting records for Ireland and Scotland in particular. For the CET, it was not quite the coldest on record but it was behind 1890 by only 0.1°C with -0.7°C. This made it the coldest of any month for the CET since February 1986 and first subzero monthly CET since then as well as the first subzero December CET since 1890. For Scotland, it was the coldest of any month since February 1947. For Ireland, it was the coldest month since January 1881.

The month was very northerly which was part of the reason why Scotland and Ireland had the coldest conditions during the month. Saying that, the month was introduced with an easterly flow continuing from an exceptional cold end to November - weirdly similar to 1890. This brought plentiful snow showers to eastern counties of Ireland and Scotland/England with as much as 21cm depth at Casement Aerodrome (Co. Dublin) on the 2nd December. Redesdale (Northumberland) had a depth of 34cm and Waddington (Lancashire) 28cm on the 1st. Sheffield (South Yorkshire) observed a depth of 38cm on the 2nd, its deepest December snow on record since records began in 1882. Altnaharra in the highlands recorded -21.1°C on the 1st which was the lowest December temperature since 1995. Mount Juliet (Co. Kilkenny) recorded a minimum temperature of -16.4°C on the 3rd which was a new December record for Ireland but this would later be beaten again in the same month and was almost 2°C colder than the previous record from 1961. The flow became more northerly during the second week before a thaw set in as high pressure collapsed during the third week of the month with milder Atlantic air feeding in over top of the ridge. This was not to last long though as severe cold air from the north was reintroduced by the 16th behind an active cold front ushering in a second big freeze. Altnaharra did not get above -15.7°C on the 22nd December, the second lowest maximum temperature on record in the UK. Ten nights during the month the temperature dropped below -18°C somewhere in the UK. Castlederg (Co. Tyrone) recorded -18.7°C on the 23rd which was a new record for December in Ireland. Straide (Co. Mayo) got down to -17.5°C on Christmas Day which was a new record for December in the Republic of Ireland and lowest for any month since January 1979. Cavan didn't get above -9.8°C all day on 21st December which was the lowest maximum temperature on record in the Republic of Ireland whilst Edenfel (Co. Tyrone) did not get above -11.1°C on the 23rd setting a new record for the island as a whole. Mount Dillon (Co. Roscommon) recorded 208 consecutive hours below freezing from 17th to 26th December. I could go on and on with so many temperature records set, it was crazy. It is no wonder why this month is held in high regard if it was this exceptional and in the era of climate change with so many warm records set rather than cold records makes it ever more exceptional to me.

There were many snow showers for eastern counties of Ireland and northern parts of the UK during pre-Christmas week whilst less so for southern parts of the UK where they were sheltered but it was very cold everywhere. Casement Aerodrome woke up to a depth of 27cm on Christmas morning which is the only Christmas Day where snow cover has been observed at a synoptic station at 9 a.m. since 1961 in Ireland.

NCEP 500mb height reanalysis for 1st December 2010 showing a snowy and cold easterly flow across the UK & Ireland.

500mb height reanalysis for 16th December 2010 showing monsterous 👺 Greenland blocking and an active cold front about to send severe cold arctic air southward over the UK & Ireland.

I have not given every single December cold spell/snow event that has occurred in the history of the UK & Ireland since reliable data began but I have discussed some of the most exceptional ones we have had along with some other interesting ones statistically along the way.

I hope that you have enjoyed this post as a lot of thought went into it. Apologies I couldn't make it any shorter. I cut out some cold spells intentionally such as 1976, 1990, 1996 and 2017 to make it somewhat readable without snoring yourself to sleep.

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