UK 2021 summary

The year began on a cool note with one of the cooler winters of recent times but it wasn't exceptionally cold by historical standards. In contrast to winter 2019-20, 2020-21 was dominated by a negative Arctic Oscillation with a frequently weaker than normal stratospheric polar vortex which meant the jet stream tended to meander more than usual but not too far south to lock the UK into a big freeze with the exception of the second week of February which brought the coldest February temperature since 1955. There was a sudden flip after mid-February to a much milder pattern that would culminate in exceptionally mild conditions a week or so after the very cold conditions and would continue into March with late March bringing some of the warmest March weather since 1968. Another change occurred in early April when we seen mid-Atlantic ridging return with northerlies advecting unusually cold air a long way south through the first half of April. Whilst the second half of April wasn't as cold as the northerlies were cut off, widespread frosts continued and resulted in the coldest April since 1986. This unusually cool weather continued into May but unlike April which was very dry, the jet stream brought frequent areas of low pressure across the UK and May was another cool month - the coldest May since 1996. The pattern yet again changed to a much warmer one by late May with ridging from the Azores which would lead into a very warm first half to June but the second half showed a complete deterioration for England & Wales with several days of heavy rainfall whilst the north and west tended to stay on the dry side closer to high pressure. Much of July was on the unsettled side - notably so in the south, but there was a heatwave mid-month with a new all-time maximum temperature record set for Northern Ireland.

January. A relatively cool month, particularly in Scotland where it was among the coldest Januaries of the past 50 years. The CET was 3.1°C which made it the coldest January since 2010 - the UK mean temperature was similar. The cold spell that began in late December continued up to mid-January, which was the most prolonged spell of colder than average conditions since early 2013. This spell brought periods of snowfall to various low level towns and villages at times but there was no widespread severe snowfall event with the air not being that cold. It turned milder from the south on the 10th but it stayed cold in the north. Storm Christoph brought very wet and windy weather between the 19th and 21st including 132.8mm at Honister Pass (Cumbria) in the 24-hour period ending at 0900 GMT on the 20th. A northerly airflow re-established by the 22nd bringing wintry showers to places and frost with a more general snow event for the west and Midlands on the 24th including the max snow depth of the month of 32 cm at Trassey (County Down) on the 25th. Milder Atlantic air associated with slow-moving fronts brought a fair amount of rain to southern regions during the last few days of January but it remained cold in the north yet again with further snow at times. The highest temperature of the month was 14.2°C at Pershore College (Hereford & Worcester) on the 28th whilst the lowest temperature was -13.0°C at Dawyck Botanic Garden (Peeblesshire) on the 9th and Braemar (Aberdeenshire) on the 31st. It was a largely unsettled January with well above average rainfall for much of England & Wales due to the distribution of the jet stream but blocking not strong enough to keep weather systems at bay. This meant that the north tended to get various snowfall events through the month. The UK had 113% of average rainfall and it was the wettest January since 2016 but it tended to be dry in western Scotland sheltered from wintry showers and southerly tracking lows. Sunshine was slightly below the UK average with 95% of average but with marked variation including below average sunshine over most of England and Wales whilst it was well above average over Scotland and Northern Ireland. 

February. A month of contrasts with a mainly cold first half dominated by easterly winds followed by an exceptionally mild second half dominated by southwesterly winds resulting in a slightly milder than average month overall for many including a CET of 5.1°C which was still much cooler than Februaries 2019 and 2020 but not nearly as cool as 2018. The second week of the month was by far the coldest period of winter 2020-21 with a severe cold polar continental flow unleashed from the east bringing heavy snowfalls though mainly to eastern coasts due to a large cap on convection. An area of low pressure over the Netherlands (named Storm Darcy by the Netherlands Met) brought heavy snow and strong winds to the southeast corner of England. The easterly airflow intensified into the 8th with a persistent feed of snow showers off the North Sea affecting the east coast of Scotland and England. The 8th was a particularly cold day with ice day conditions for a good portion of southeast England including a maximum temperature of -1.5°C at Rothamsted (Hertfordshire), -2.4°C at Wych Cross (East Sussex) and even St. James' Park (Greater London) managed to only rise to -0.1°C all day. The 8th of February was the coldest day widely since 2018. Manston (Kent) had a max depth of 17cm on the 8th which was its deepest snow since January 1987. Further snow showers occurred in the days that followed with the cold easterly airflow continuing. A max snow depth of 42cm was recorded at Aboyne (Aberdeenshire) on the 10th. Braemar (Aberdeenshire) got down to -23.0°C on February 11th which is the lowest February temperature in the UK since 1955 and lowest for any month since December 1995. It was also the first time that -20°C has been achieved somewhere in the UK since 2010. Ravensworth (North Yorkshire) recorded an air minimum temperature of -15.3°C on the 12th which was England's lowest temperature for any month since February 2012. The stratospheric polar vortex had reintensified by mid-February after being perturbed for a long period of time since early December and resulted in a return of the westerlies from Valentine's Day with very mild conditions prevailing for the rest of February. There were strong westerly winds at times including a max gust of 83 mph at South Uist (Western Isles) on Valentine's Day with outbreaks of rain from the Atlantic but no named storms. The final week in particular was very mild with a maximum temperature of 18.4°C at Santon Downham (Suffolk) on the 24th - one of the highest February temperatures on available record but significantly lower than values seen in late February 2019. This meant that February 2021 had a monthly absolute temperature range of 41.4C (-23.0 to 18.4) which was a new February record beating a range of 40.0°C (-25.0 to 15.0) in February 1955 and the highest for any month since March 1965. Honister Pass (Cumbria) recorded 125.8mm of rain in the 24-hour period ending at 0900 GMT on the 24th. Heights rose from the south in the final few days bringing very sunny conditions for most and the weather settled down but remained mild. It was a rather wet month again for the third consecutive month concluding quite a wet winter overall with 116% of average UK rainfall for February. Sunshine was near average with 103% of average but rather below par in southern and western areas with northern Scotland well above average.

March. It was a milder than average March with a CET of 7.2°C but not as mild as 2017 and 2019. This was largely down to the second half and especially the last three days with the first week being on the cold side and the second week wasn't especially mild either but disturbed with Atlantic depressions giving outbreaks of rain and strong winds. The first week seen slack easterly winds bring relatively cool air off the continent with a lot of cloud and fog at times. The lowest temperature of the month was -8.5°C at Braemar (Aberdeenshire) on the 6th. A 958 mb area of low pressure set up shop across the northwest of the UK on the 10th and 11th giving heavy rain at first before showery conditions in behind with hail and rain showers. Further areas of low pressure pushed through the country on the 13th and 14th with a max wind gust of 99 mph at Needles (Isle of Wight) on the 13th. Pressure rose from the south on the 15th with weak fronts giving fair cloud at times interspersed with sunny spells and milder temperatures simultaneously although still relatively chilly in the east closer to a northerly flow circulating around the ridge. It became unsettled again from the 24th to 30th though rain was mainly limited to northern and western areas with heavy falls at times including 177.2mm at Seathwaite (Cumbria) in the 24-hour period ending at 0900 GMT on the 29th. It became warm during the final few days of March with a southwesterly and southerly flow bringing very mild air up from a long way south. The highest temperature was 24.5°C at Kew Gardens (Greater London) on the 30th which was indeed the highest March temperature in the UK since 1968. This temperature would not be beaten again until late May. Local records were also set including 22.6°C at Oxford (Oxfordshire) where records began in 1853 beating the previous record of 22.2°C back in March 1965. Air minimum temperatures were also unusually high with Kinloss (Moray) not getting below 12.7°C on 30th March which is an equal March high minimum temperature record for Scotland. 

April. The coldest April since 1986 with a CET of 6.4°C and the coldest on record for CET minimum (CET maximum and minimum records began in 1878) beating April 1917 (1.4°C) with a mean minimum temperature of 1.0°C. This meant that April was colder than the preceding March - the first time to occur since 2012. The first half of April was dominated by unusually cold northerly winds after the 4th with high pressure in the Atlantic ridging up to Greenland forcing the jet stream south and was a big change on the very mild to warm weather in late March. These northerly winds were accompanied by widespread frost, wintry showers and lying snow across high ground and falling to low levels in northern Scotland. Northerly winds gusted to 75 mph at Fair Isle (Shetland). The maximum temperature was only 1.1°C at Lerwick (Shetland) on the 5th whilst Loch Glascarnoch (Ross & Cromarty) did not get above 0.7°C all day on the 6th where a snow depth of 12cm was also reported on the 7th. This cold moderated by the 8th temporarily but a northerly flow was reintroduced by the 9th with yet more wintry showers and widespread frosts. There was 4cm of snow at Buxton (Derbyshire) and 3cm at Leek (Staffordshire) and Thorncliffe (Staffordshire) on the 11th. The lowest temperature of the month was -9.4°C at Tulloch Bridge (Inverness-shire) on the 12th which was the lowest April temperature in the UK since 1978 and a joint daily record low for 12th April. By the 14th, pressure rose over Scandinavia and cut off the northerly flow but was replaced with an easterly flow instead. Anticyclonic easterlies were the theme for the next 10 days with plentiful sunshine across the country so days warmed up to an extent but nights continued on the cold side with further frosts. Retrogression of the high took place again by the 26th out west with Greenland blocking returning and a northerly to northeasterly flow setting in bringing showers and a drop in temperatures. The highest temperature of the month was 21.4°C at Treknow (Cornwall) on the 1st as the mild weather held on by its fingertips in the southwest of the country - this was the first time that the April monthly absolute max was lower than the preceding March absolute max in the UK since 2012 and the lowest April max since 2016 (the first April to not achieve 25°C since too). It was the frostiest April on record for the UK (records since 1960) with a national average of 13.8 air frosts during April 2021 beating 10.5 air frosts in April 1970. There were 6 days during the month where at least one station somewhere in the UK recorded -7°C or lower - some winter months before did not even have one single day of such. There was also 15 days where somewhere recorded -5°C or lower - the most in a spring month since March 2013 and the most in any month since January 2019. It was an exceptionally dry April - the fourth driest since 1862 - with only parts of Wiltshire and northern Scotland exceeding 50% of average rainfall. It was the sunniest April on record for the second consecutive year in the UK (records since 1919) - it was also the sunniest on record for Wales, Scotland and Northern Ireland. This is the first known instance of where a monthly sunshine record has been broken for 2 years consecutively in the UK.

May. Another colder than average month - the coldest May since 1996 with a CET of 10.1°C. It was the coldest April/May combination for the CET since 1941 and was the first time since November/December 2010 that there were two consecutive months with an anomaly of a degree below the 1961-90 average. Mean maximum temperatures had greater anomalies below average than mean minimum temperatures with places seeing mean maxima up to 2°C below average. Unlike April, May was much wetter. For the long-term England & Wales Precipitation series with records since 1766, it was the 7th wettest May on record and wettest since 1967 with 122.7mm of rain. The UK as a whole had its 4th wettest May since 1862 with 171% of average and only parts of western Scotland had near or below average rainfall. The max daily rainfall was 103.0mm falling at Mickleden (Cumbria) in the 24-hour period ending at 0900 GMT on the 21st. There was even a bit of snow in northern places around the 5th/6th though mainly over high ground with a 1cm depth at Achiltibuie (Ross & Cromarty) on the 5th. The month was characterised by Greenland blocking with a southerly tracking jet stream bringing frequent areas of low pressure across the UK. In clear skies further north, there were several instances of unseasonably cold nights with the lowest temperature for the month of -6.1°C being recorded at St Harmon (Powys) on the 2nd but May 2020 had a lower absolute minimum temperature. The month ended on a much warmer note with high pressure setting up over or close to the UK. For a while, there were talks of March holding the spring absolute maximum temperature for the first time on known record - 1968 was close but the April max equalled the March max that year with both achieving 25.6°C. However, this was put to rest by the final day of May with Kinlochewe (Ross & Cromarty) recording a maximum temperature of 25.1°C. Sunshine was rather below average for most of the country except Northern Ireland and was well down on values from May 2020 which was the sunniest month on record for large parts of the south. England had its dullest May since 2007 with only 165.8 hrs of sunshine. It was an unusually thundery May with lightning reported over the UK and or Ireland every day from 26 April to 20 May and was provisionally the most thundery May since 1983. A deep depression on the 3rd brought a max wind gust of 93 mph at Needles Old Battery (Isle of Wight).

June. A pretty warm month on the whole but with contrasting halves - an exceptional warm first half, particularly for the south, followed by a much cooler second half although it stayed warm in the north at times. It was the warmest June since 2018 with a CET of 15.5°C and provided a fair contrast to April and May. High pressure sat mainly over and to the south of the country during the first half of June bringing largely settled and persistently warmer than average conditions but southwesterly winds around the top of the high fed in a fair bit of cloud to northern areas at times along with outbreaks of rain towards mid-month whilst further south sunshine was aplenty. The highest temperature of the month was 29.7°C at Teddington Bushy Park (Greater London) which was the lowest June max temperature in the UK and first time that a June has failed to achieve 30°C since 2016. From the 17th, there was a dramatic cool down with localised thunderstorms and torrential downpours in the southeast of England resulting in flooding. Maximum temperatures were well below average here by the summer solstice on the 21st which was colder than the prior winter's solstice (December 21st) for some and possibly the coldest summer solstice since 1977. Wych Cross (East Sussex) did not get above 11.8°C all day on 21 June 2021 whilst it achieved 12.3°C on 21 December 2020. There were also some cold nights around this period with the lowest temperature of the month being -2.4°C at Altnaharra on the 22nd - this was the lowest June temperature seen in the UK since 2012 and potentially the lowest for so late on since 1981. There were further thunderstorms in the south and east of England during the final week of June but high pressure brought settled conditions almost throughout to the north and west of the UK and June overall had 59% of average rainfall for the country. Scotland had its driest June since 1988 with only 44% of average whilst Northern Ireland had its driest June since 2006 with 52% of average rainfall. The highest daily rainfall of the month was 74.0mm at Princetown (Devon) in the 24-hour period ending at 0900 GMT on the 28th. Sunshine was above average for northern and eastern regions and slightly below average for some western fringes with 107% of average sunshine for the UK as a whole - this masks some very dull conditions in the second half in southeast England.

July. A very warm month overall but with some very divided periods - a wet first fortnight (particularly over England) with mild nights followed by a heatwave period mid-month then a very cool and wet end. The CET for July was 17.7°C which was equal to July 2014 and warmest since 2018. It was the joint 5th warmest July on record since 1884 for the UK as a whole. Mean maximum temperatures were up to 3°C above normal in western Scotland and Northern Ireland but much closer to normal in eastern counties of England while mean minimum temperatures were well above average for most areas and it was the joint 2nd warmest July on record since 1884 for UK mean minimum temperature. In the long-term CET series (minimum records since 1878), it was the joint 5th warmest July on record for mean minimum temperature and warmest since 2006. This follows on from a pretty mild June too for mean minima and was the 2nd warmest June-July combination on record since 1884 for England and Scotland whilst it was the 3rd warmest for the UK as a whole. This was a huge contrast to the prior April and May. It was the 3rd warmest July on record since 1884 for both Scotland and Northern Ireland, behind only Julys 2006 and 2013. A heatwave developed by the third week of July from the ascendancy of high pressure from the Azores importing tropical continental air by the 17th. Ballywatticock (County Down) recorded 31.2°C on the 17th which at the time was a provisional new record maximum temperature for Northern Ireland but it has been disregarded due to not passing quality checks, Killowen (County Down) recorded 30.8°C on the same day which was a joint all-time record for Northern Ireland with June 1976 and July 1983. This was the first 30°C of the year in the UK and there hasn't been a previous year known to achieve the first 30°C in Northern Ireland - although the first 30°C of 2013 was achieved in the Republic of Ireland. This was the latest date for the first UK 30°C of the year since 18 July 2016. Subsequently, the Ballywatticock value would be broken twice with 31.3°C at Castlederg (County Tyrone) on the 21st and 31.4°C at Armagh Observatory (County Armagh) on the 22nd - the Armagh Observatory figure also did not pass quality checks and therefore, the Castlederg value is a new all-time maximum temperature record for Northern Ireland. Northern Ireland had up to 4 days in July 2021 of achieving a maximum temperature of at least 30°C which was the most on available record beating 3 days in June 2018. The highest temperature of the spell and month was 32.2°C at Heathrow (Greater London) on the 20th which was the joint lowest (with 2017) July UK max temperature since 2012 - a reflection of just how high July maxima have been recently. The UK overall had 93% of average rainfall but the south had a very wet month due to spells of heavy rain and thunderstorms at times in the first and final weeks whilst the north was drier away from the Scottish highlands. 87.9mm fell at Bethersden (Kent) in the 24-hour period ending at 0900 GMT on 26th July. The depression on the 30th was named Storm Evert - the first July named storm since storm naming began in 2015-16 - and brought a max wind gust of 77 mph at Needles (Isle of Wight) which was the highest July gust since 1998. Sunshine was above average for western areas - particularly Scotland - but below in the east and well below in the Northern Isles with 111% of average overall for the UK. 

August. A drier than average month overall with 73% of average rainfall (making it the driest August since 2003 reflecting the often wet or changeable nature of Augusts since) but with a mostly unsettled first half with plentiful rain between the 5th and 13th including a daily rainfall of 74.2mm at Spadeadam (Cumbria) in the 24-hour period ending at 0900 UTC on the 9th. A wind gust of 51 knots (59 mph) was recorded at Needles (Isle of Wight) on the same day. Apart from the 20th and 21st when a depression brought heavy showers, the second half was drier and warm in the north, particularly western Scotland in the final week where it also tended to be very sunny sheltered from the northeasterly winds circulating around the high pressure. The south and eastern coasts were much cooler and cloudier most of the time with a max temperature of 26.4°C at Cavendish (Suffolk) on the 15th - this was the lowest August monthly max temperature in England since 1986. Unusually, the highest temperature of the month was achieved in Scotland with 27.2°C at Tyndrum (Perthshire) on the 25th - the first time the August monthly max temperature was recorded in Scotland since 1931. Mean temperature was very close to average for August for the UK but the south was cool whilst the north was relatively warm due to the final week. The CET for August was 15.8°C - coolest since 2017 whilst mean maxima were the lowest since 2014. It was a very cloudy month away from western Scotland. Parts of central and eastern England had their dullest August on record whilst for others it was the dullest since 1968 or 2008. Sunshine for the UK as a whole was 79% of average and the dullest August since 2008. 





* Averages refer to 1981-2010.