Nature Menu

Introduction Beginner's Guide Where to find wild flowers Where to find butterflies Books and online tools Week by Week Nature Blog SWC_Nature

Nature and Weather in South East England

This Week Message

For the latest observations, see the Nature Blog or the @SWC_Nature Twitter feed.

December weather

Other weather pages: JanuaryFebruaryMarchApril • MayJuneJulyAugust September • OctoberNovember

Return to December nature

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.

Wet and windy starts to December are not unusual – this was true in 2002, 2003, 2006, 2007 and 2009. On 7 December 2006 there was even a tornado in Kensal Green, London. Temperatures during this time can be remarkably mild – as much as 11-13 degrees in 2006, for example, though 7-8 degrees might be more typical.

Some Decembers then remain dominated by westerly winds throughout - as was the case in 2011 when there were was very little really cold weather and night temperatures only once or twice dipped below freezing. This was a grey month, with quite a bit of rain, though also scattered sunny days.

2015 was even milder - the warmest December on record - 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. There were severe floods in the north of England but in the south rainfall was fairly moderate.

The halycon days

By contrast, sometimes high pressure dominates the whole month, as in 2001 and 2005 when the weather was predominantly sunny throughout December. In 2005, for example, the month had over 20 sunny days and only four days with rain, leaving reservoirs in the south east of England very low after a relatively dry autumn.

2008 also saw highs dominating, with temperatures of just 3-4 degrees by day and hard frosts overnight – the coldest December in thirty years, according to some reports. 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 2014 the south east was on the boundary between a continental high to the south and a large low centred over Iceland, 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 Deccember), with night temperatures down to -5 degrees on the last of these.

In 2016 there was again a high to the south and active lows to the north from the 6th to the 12th, with the south east on the boundary. 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 other Decembers high pressure sets in from around 17 or 18 December (these are the original ‘halcyon days’, incidentally – a period of fine weather around the winter solstice noted by the ancient Greeks). Whether the high pressure brings sunshine and frosty nights, or just grey skies depends on where the high pressure is and the direction of the wind.

A good example was in 2007, when high pressure set in for a longer than usual time – from 10 to 21 December - and produced a good number of frosty, sunny days, but also some gloomy grey ones as the high pressure zone wriggled around over the near continent. In 2006, high pressure from 17 to 23 December resulted in thick fog from the 20th to 22nd, disrupting flights at Heathrow.

2012 seemed to be the reverse of these years. Until 17 December the weather was fairly bright, 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 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.

Say it ain't snow

Snow is unusual the south east in December, Christmas cards showing snow-bound countryside notwithstanding. But there are exceptions. One was in 2005 when northerly winds down the east coast dumped several centimetres of snow on Kent on 27 December which remained on the ground for several days.

Even more notable were 2009 and 2010, both of 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 remained 2 or 3 degrees at best, as low as minus 3 degrees in London at night, and as low as minus 10 degrees in rural areas. The snow did not melt, remaining on leaves and branches even in the sunshine.

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 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.

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. In 2006, 27, 28 and 30 December all saw partial sunshine, while New Year’s Day was also sunny. In 2008, there was sunshine from 26 to 30 December, and in 2009 there was sun on the 27th and 28th. Despite deep westerly lows, 2013 also managed to be sunny on Christmas Day itself, and on the 28th and 29th and the afternoon of the 30th. 2014 was an almost exact copy, the difference being sunshine all day on the 30th and to the west of London on the 27th. In an otherwise very cloudy December 2015 the 27th, 28th and 31st nevertheless managed to be sunny, and 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). By contrast in 2007 only the 29th was sunny, in 2010 only Boxing Day, and in 2011 only the 28th. Christmas 2012 saw very wet and windy weather throughout, with only a few fleeting sunny periods between deep lows.

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, incidentally, 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. One sees a photo of the countryside taken in summer and it is a shock how bright and cheerful everything looks.

Even early in the month, the sun is so low that the shadow of one tree stretches right across the park 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.

Other weather pages: JanuaryFebruaryMarchApril • MayJuneJulyAugust September • OctoberNovember

Return to December nature

© Peter Conway 2006-2017 • All Rights Reserved

No comments:

Post a Comment