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Warm but dull month for December 2021

December 2021 kicked off meteorological winter with a broadly warm – albeit dull – month of weather, during which the UK reached its highest New Year’s Eve temperature on record, with 16.5°C at Bala (north Wales). Maximum temperatures also exceeded 15°C in all four nations. This is according to provisional figures released by the Met Office.  

The unusually high temperatures seen on New Year’s Eve coincided with a temperate end to December, resulting in some stations breaking long-standing one-off records for the month. Cromer in Norfolk saw its warmest December day in a 103-year series with 15.4°C recorded on 30th December. 

For the complete month, it’s the notably high minimum temperatures recorded in December that stand out from the statistics, especially in southern areas. The UK had an average minimum temperature in December of 2.8°C, which is 1.4°C above the 1991-2020 long-term average; figures that have recently been updated to reflect the latest 30-year meteorological period. The highest average minimum temperature seen in December stands at 5.2°C, set in 2015.  

For southern areas, minimum temperatures were even further from the meteorological averages, with southern England seeing average minimum temperatures at 4.3°C, which is 2.0°C above the long-term average for the month. There were some exceptionally mild nights, with overcast conditions and a south-westerly flow drawing air from the Azores. Daily minimum temperatures on New Year’s Eve remained widely in double figures, with several stations including Sheffield, Bradford and Buxton recording their highest daily minimum temperature on record in series of over 100 years – around 10°C higher than the December average. 

Map showing the average minimum temperatures for the UK in December 2021. The map shows above average minimum temperatures for much of the UK, especially in the south.

Average minimum temperatures versus the long term average for December 2021

The often mild, cloudy nights resulted in below average days of frost for the much of the UK. There was an average of just 11.5 days of ground frost reported across the UK in December, well below the long-term average of 16.3 days. The fewest average number of days of ground frost in December was in 2015, with just 5.8 days.  

Map showing below average days of ground frost for the UK for December 2021. The map shows especially low numbers of ground frost days in the south.

Average number of ground frost days in the UK in December 2021 versus the long term average

Despite the relatively high temperatures, sunshine hours in December 2021 have been in short supply, with an average of just 27.6 hours for the UK, less than one hour per day on average and only around two-thirds of the normal December sunshine total. That’s little enough to make it the dullest December since 1956, when an average of 19.5 hours of sunshine was seen. It was also the UK’s sixth dullest calendar month in records from 1919. England saw 60% (30.6 hours) of its average sunshine, Wales 69% (28.3 hours), Scotland 79% (23.6 hours) and Northern Ireland only 54% (20.7 hours). 

The dull but warm conditions have provided an unusual mix for the country’s gardeners. Chief Horticultural Advisor at the Royal Horticultural Society Guy Barter yesterday said:

“After milder weather and limited frosts so far this winter, greens such as Brussels sprouts and leeks have kept growing and winter flowers such as autumn flowering camellia and Christmas roses have not been spoilt.  

“Weeds too have kept growing but with dull conditions they won’t set seeds and can be spared for now to help wildlife. Lawns remain remarkably green but growth has been limited by a lack of light, so the lawnmower can rest a bit longer.” 

A map of the UK showing below average sunshine duration for December for much of the UK.

Sunshine duration for the UK versus the long term average for December

Rainfall was relatively near average for much of the UK, although areas in the northwest generally saw less than their average. Northern Ireland received 113% (136.6mm), whereas Scotland received 79% (136.8mm). The UK had 90% of its average rainfall (115.1mm).  

Map of the UK showing rainfall versus the long term average for the month. The map shows near-average rainfall for much of the UK, although slightly below average in the northwest.

Mike Kendon from the National Climate Information Centre yesterday said:

“December will largely be remembered for the unseasonable warmth we saw in the middle and end of the month. As a result, we have seen relatively few days of ground frost and air frost and less of the cold weather that you’d normally expect at the start of winter, although some northern spots have seen some hard frosts. There were also remarkable temperature inversion conditions for several days in Scotland where the warmest and sunniest place to be was across the mountain summits. 

“This spell of weather in the middle of the month was driven by an established area of high pressure over the UK, keeping temperatures well above average for spells, although low temperatures did take charge in the early part of December.”  

December 2021 also saw a white Christmas declared by the Met Office, with a flurry of snow over high ground in the north of the UK. 

Check the Met Office website for a full round-up of 2021’s year in weather.

Provisional December 2021 Mean temp (°C)   Sunshine (hours)   Rainfall (mm)  
  Actual  Diff from avg (°C) Actual % of avg Actual % of avg
UK  5.3  1.1  27.6 65   115.1  90
England  6.1  1.4  30.6 60  88.6  96
Wales  6.4  1.5  28.3 69  184.4  105
Scotland  3.4  0.4  23.6 79  136.8  79
N Ireland  6.1  1.4  20.7 54  136.6  113

 

 

Channel website: http://www.metoffice.gov.uk

Original article link: https://blog.metoffice.gov.uk/2022/01/04/december2021weather/

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