December weather

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December weather is at its best when it is cold and crisp – days of hard frost and deep blue skies, when the ground is frozen solid and all seems magical. On clear nights, the stars glitter brightly, and the moonlight reflects eerily off the frosted grass. At such time winter seems just wonderful.

But often the weather is just plain grey and depressing, and the ground tediously muddy. It can be rainy and miserable if westerly winds establish themselves, but the signature conditions in December seem to be dry, not too windy, but with grey gloomy clouds. Urban dwellers turn with relief to the cheerfully lit streets of the city. Along with short days, these make the state of the weather seem of lesser concern.

Some Decembers are dominated by westerly winds throughout - as was largely the case in 2023, when the weather was predominantly grey. There was rain on 14 days, only two days of full sunshine, and seven others with part sunshine. Temperatures - both by day and by night - were mainly in the 8-12 degree range, getting as high as 15 degrees on Christmas Eve. Only three days early in the month saw night-temperatures below freezing There were two periods when high pressure tried to establish itself, bringing more northerly winds, but none lasted more than three days.

2015 was the warmest December on record up to that point, with strong westerly winds throughout bringing rapidly moving clouds and only fleeting glimpses of sun (only four days were sunny, three of them between Christmas and New Year). Temperatures stayed at 11-14 degrees by day and often just a degree or two colder at night, only dipping down to 4 or 5 degrees at night on a handful of occasions. All sorts of early spring flowers came out, including snowdrops, daffodils and dandelions.

2011 was another mild and grey December, with very little really cold weather and night temperatures only once or twice dipping below freezing. There was quite a bit of rain and only scattered sunny days.

A mix of highs and lows

In most years there is a mix of highs and lows, however. In 2021, for example, cold north westerly winds due to a low centred to the north east brought a mixture of sunny and cloud in the first five days. But otherwise westerlies dominated and it was a very gloomy month, with 23 days having no sunshine at all. There were 11 days with rain and six more with drizzle. Even when high pressure set in from the 14th to the 21st, it just brought unbroken cloud. The last three days of the month were very mild, with air from the Azores producing daytime temperatures of 15 degrees. New Year's Eve was the warmest ever, topping 15.8 degrees in one location in Somerset.

In 2020 the middle two weeks were mild, with westerly winds, and temperatures reaching 11-13 degrees by day. The period included three days of full sunshine and three with part sunshine. The first week was colder and more mixed, however, with some sunny periods and fog, some nights getting close to freezing, but also some rain. High pressure then set in for the last week of the month, bringing colder northerly air with some sun but mostly grey skies, interspersed with a deep Atlantic storm, whose rain largely fell on the night of 26-27 December.

In 2019 the month started with four days of high pressure, three of which were sunny. Westerlies then dominated up to Christmas Eve, often with a static low centred to the north or north east of the UK, before a continental high developed for the last week of the month. This was quite a wet December, with rain on 15 days, and widespread flooding in the south east by the end of the third week. There was even a small tornado in Chertsey on the 21st. But there were also nine days of sun overall and eleven with some sun.

In 2018 there were westerlies from 1 to 8 and 15 to 22 December, a Scandinavian high from the 9th to the 14th, and more high pressure from the 23rd onwards. There was rain on 11 days but full sunshine on five days and some sunshine on ten more.

In 2016 there was a high to the south and active lows to the north from the 6th to the 12th. From 13 to 16 December there then was a blocking high to the east with a low static over the UK, and from the 19th to the 25th full westerly winds, with storms in Scotland as Christmas approached. In the south east throughout this period there was damp, mostly cloudy, but relatively mild weather with temperatures from 8 to 13 degrees. The month finished with four frosty sunny days from 26 to 29 December (up to 8 degrees by day but minus 4 or 5 at night), having also started with five days of similar weather.

In 2014 there was a continental high to the south and a large low over Iceland and the south east was sometimes in one system and sometimes the other. There were 12 fully sunny days, six that were at least half sunny, and it rained (usually short showers) on 12 days. There were four sunny Saturdays in a row (starting on 29 November: Saturday 27 December was also sunny to the west of London) and four frosty sunny days over Christmas (25, 28, 29 and 30 December), with night temperatures down to -5 degrees on the last of these.

In 2012 the weather was fairly bright until 17 December, with high ridges alternating with lows and plenty of sunny but frosty days. Temperatures were sometimes just a few degrees by day and down to minus 5 overnight in the countryside, but there were slightly milder (8 degrees or so) interludes in between. On 12 December there was a freezing fog overnight producing a magnificent hoar frost (tassels of frost on twigs and leaves) which lasted in part through two magnificent sunny days. But from 18 December the weather turned very wet and windy, albeit with mild 11 degree temperatures, and remained so for the rest of the month. There was major flooding in the West Country and 2012 was declared the wettest year on record in England.

2013 was very similar to 2012, with high pressure largely dominating till the 12th, though with relatively mild temperatures of 8-11 degrees, and decent amounts of sunshine. The 11th and 12th saw thick fog persisting all day in places, but clearing to glorious sunshine in others. Westerlies then set in on the 13th bringing deep lows and - as Christmas approached - flooding. There was particularly heavy rain on the 21st and the 23rd, with the rain lashing down on the latter day for almost 24 hours. However, there were good gaps in this weather too, with 19, 20, 25, 28 and 29 December all sunny, and the 27th sunny in the afternoon.

Occasionally, high pressure dominates

In the past, high pressure sometimes dominated he whole month, though this has not happened for over a decade - perhaps due to climate change, which is predicted to make our winter weather wetter and windier.

December 2010 and the second half of December 2009, when high pressure brought snow, are discussed in the next section. 2008 also saw highs dominating, with temperatures of just 3-4 degrees by day and hard frosts overnight – the coldest December in thirty years, though that record was soon broken in 2010. There were 12 fully sunny days in the month, and another eight had some sunshine. It turned mild – up to 13 degrees - from 17 to 25 December – but then the month ended on a very cold note again.

In 2001 and 2005 high pressure also lasted much of the month. 2005 saw 20 sunny days and only four days with rain. This left reservoirs in the south east of England very low after a relatively dry autumn.

Highs do not always mean sunshine: it depends where they are positioned. 2010 and the second half of 2009 saw a mix of sun and cloud, while in 2018 high pressure to the south of the UK from 23 December onwards only produced two days of sun, with the rest cloudy. A high centred over the UK from 14 to 21 December 2021 brought nothing but thick cloud. In 2006, high pressure from 17 to 23 December resulted in fog from the 20th to 22nd, disrupting flights at Heathrow.

Say it ain't snow

Snow is unusual the south east in December, Christmas cards showing snow-bound countryside notwithstanding. But there are exceptions. In 2022 static highs over Scandinavia (later Russia) and Greenland kept the UK trapped in northerly easterly and then northerly airflows up to 17 December. At first this brought frost and frozen ground - including three magical sunny days from the 6th to the 8th (when there was also a sparkling full moon, almost vertically overhead), and hoar frost on the 11th (a Sunday). But then on the evening of the 11th several centimetres of snow fell in parts of Kent, Surrey and Sussex and up to 12 centimetres on the northern edge of London.

Continued northerly airflows then kept this snow unmelted - even on twigs and branches in many cases - for the whole of the next week, which included four sunny days. There was also the quite rare phenomenon (for this part of the world at least) of surface hoar, the frozen version of dew - elongated ice crystals forming on lying snow, creating a pile carpet effect. The thaw came on 18 December, and the rest of the month was dominated by westerly lows, producing plentiful rain.

Also notable was 2009, which saw substantial December snowfall, due to persistent high pressure to the north and west of the UK. In 2009 this set in on 13 December, bringing easterly winds, and sleet on the 16th, 2cm of snow on the 17th, and 10-12cm of snow (up to 20cm in Kent) on Friday 18th. There then followed a glorious weekend, when the sun shone but temperatures reached 2 or 3 degrees at best, and the snow did not melt, remaining on leaves and branches.

There was another centimetre of snow to the north of London on the evening of 20 December 2009, and big snow fall causing major disruption in Hampshire, Berkshire and the Chilterns on 21 December. Temperatures remained cold, with the snow unmelted even on 23 December and a widespread hoar frost. Slightly milder air started the thaw that evening, but snow still lingered on the ground until Christmas Day in places. The south then had no further snow in December, though it continued further north, and on 29 and 30 December there was very cold rain in the south east that fell as sleet or snow in the Midlands.

2010 saw snow even earlier, in what was said to be the coldest December for a hundred years. There was 3cm of snow in London on 30 November, and a further 10cm the following day in Kent, Sussex and Surrey. The snow stayed on the ground for the first three days of December, even on pavements in central London, with temperatures minus 2 at best by day, minus 5 at night and down to minus 10 in the countryside. Temperatures then edged up and were at 6-7 degrees from 10 to 15 December, but some rural areas still kept snow.

There was then almost an exact repeat of the previous year - sleet on 16 December, 1cm of snow on 17 December, and a big fall of 10-15cm on Saturday 18 December. This brought particular chaos to Heathrow airport, where flights were cancelled for days on end, dominating national news. Again, temperatures were minus 1 or 2 by day, as much as minus 5 by night in London, but with minus 11 widely recorded in the countryside on 20 December and minus 19.6 degrees in Chesham in the Chilterns. Once again this meant the snow remained on the ground (and for some days also on twigs and branches), only partially thawing on 22 December, and remaining in many places over Christmas. A partial weakening of the high to let in westerly winds finally produced a thaw on 27-30 December.

In the two following years there was minor snowfall. In 2011 there was 2cm of snow in the Chilterns on 16 December, and in 2012 a similar amount fell on Essex and Hertfordshire on 4 December, with a dusting in London. But in both cases the snow rapidly melted.

In 2017, another December in which alternating highs to the south west and lows further north and east brought some sunny cold days and some milder cloudy ones, a low moving into cold air on the 10th brought 6-8 centimetres of snow to the London area. Most of this quickly melted, but on higher ground to the north of the city it stayed on the ground for three days, very slightly thawing on the 11th, then setting solid that night, so that on the 12th the ground was covered with hard icy snow. On the 21st westerlies then set in for a mild but cloudy Christmas.

There was also snow in Kent and Essex on 4 December 2020, as well as quite extensive snow in the Midlands in the last few days of the month, which reached as far as Oxfordshire, but never got to the south east. Meanwhile in 2005 northerly winds down the east coast dumped several centimetres of snow on Kent on 27 December which remained on the ground for several days.

After Christmas

Most years, however, Christmas is neither white nor wet, but just grey. The period after Christmas has quite a good record for producing sunny days. however.

For example, Boxing Day was sunny in 2020, 2022 and 2023. In 2020 Christmas Day and the morning of the 24th were also sunny, while in 2022 the Boxing Day sunshine extended to the morning of the 27th. In 2017 it was the afternoon of Boxing Day and all of the 27th that was sunny, while in 2018 there was sun on the 24th and 27th. In 2019 Christmas Day saw perfect blue skies, as did the 29th and 30th, while the 23rd and 24th had a mix of sun and cloud.

In 2016 it was sunny from the 26th to 29th, even though fog was forecast for the last two of these days (on the 30th it finally was foggy), and in an otherwise very cloudy December 2015 the 27th, 28th and 31st nevertheless managed to be sunny. Despite deep westerly lows, 2013 also managed to be sunny on Christmas Day itself, and on the 28th, 29th and the afternoon of the 30th.

More disappointing years include 2021, which was very grey, with light rain or drizzle, and only a little bit of sunshine on the afternoon of the 28th and 29th. Meanwhile in 2012 Christmas was very wet and windy weather throughout, with only a few fleeting sunny periods between deep lows.

The shortest day

The 21st is the shortest day, of course, but it is not the day with the earliest sunset: that actually occurs from the 10th to the 14th, when sunset (in London) is at 3.51pm. It then creeps later, reaching 3.56pm by Christmas Day and 4.01pm by the end of the month. By this time, there is actually useable light until 4.30pm.

By contrast, dawn continues to get later right up to the end of the month. On 12 December it is getting light at 7.57am, but by Boxing Day that has crept forward to 8.06am and it remains that late until 5 January. This is the time when you wake in the dark and are amazed to discover it is nearly 8am. By 17 January it is still only getting light at 7.58am, while dusk is at 4.24pm, with useable light nearly till 5pm.

The reason for this difference between the earliest sunset and latest dawn is that the solar day - the time it takes the sun to be in the same place in the sky as it was the previous day - varies slightly throughout the year. It is slightly longer than 24 hours at the solstices and slightly shorter at the equinoxes. This means that our clock time gets slightly out of alignment. As the winter solstice approaches, the dusk is still getting slightly earlier relative to midday, but the solar day is still getting slightly longer - that is, shifting later in our clock time.

These two effects counteract each other so that in our clock time dusk no longer appears to be getting earlier after 12 December and soon starts to get later. By contrast, the dawn is still getting slightly later relative to midday as the solstice approaches and clock time is also getting slightly later each day as the solar day lengthens, so our clocks show dawn still getting later. Only on 6 January is this effect sufficiently reversed for clock time dawn to start getting earlier (from 8.06am to 8.05am London time).

Whatever, in December one has almost got used to the short days and long nights. The days when one could be out in the light till 8pm, or wear only a short sleeved shirt or lie on green grass, seem so distant as to be almost dreamlike. Looking at a photo of the countryside taken in summer, it is a shock how bright and cheerful everything looks.

Throughout the month, the sun is so low - just 15 degrees above the horizon at best - that the shadow of one tree stretches right across the park even at midday. By 1.30pm it is below treetop level. The low angle of the sun means it is easy for it to be obscured by low clouds on the horizon, even if there are blue skies overhead. But if the horizon is clear, December can produce the most magical of dusks. Though the low sun shines into your face, you do not feel the need to shade your eyes. Somehow every drop of sun you can soak up at this time of year seems precious.

In contrast to the low sun, the moon is at its highest in December, seeming to be almost vertically overhead. This makes for entrancing scenes in the countryside, especially on frosty or snowy nights.

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