December provided a wide variety of weather types with many interruptions to the westerlies that had dominated so much of 2017. The month started quietly with a ridge of high pressure crossing southern areas. In the second week high pressure built to the west of the UK allowing a cold north-westerly flow to develop. On the 10th, fronts moving north-east ground to a halt over southern Britain giving widespread snow. Westerly winds returned from mid-month to Christmas. It then became colder with further slight snow on southern hills on the 27th. The jet stream was now to the south of the UK and this brought a succession of lows across southern Britain, giving a wet end to the month.

Temperatures

The average Central England temperature was 4.8°C making it the equal coldest December since 2010 but nevertheless 0.2deg C above the 1981-2010 average. The equivalent figure for Scotland was 3.8°C, 0.7deg C above average, but western coasts were around average. The movement of the jet stream meant that there was a mixture of cold and mild spells – the run-up to Christmas was very mild and Cassley (Sutherland) reached 15.2°C on the 19th. By contrast, overnight, -13.0°C was recorded at Dalwhinnie (Highlands) on the night of 10th to 11th and also at Shawbury (Shropshire) the following night.

Snow falls in northern UK after one of coldest nights of 2017 Read more

Rainfall

The average rainfall across England and Wales was 97mm, 107% of average. Rainfall was a little below average in Scotland, northern England and Northern Ireland. A notable daily rainfall was one of 43mm in west Norfolk in the 24 hours up to 6pm on the 27th. This was associated with the passage of an active low over southern Britain which was responsible for one of the two snow events in southern Britain, the other being on the 10th. The latter gave 10cm-30cm across much of the western Midlands and mid Wales.

Sunshine



With relatively few cloudy west and south-westerly airflows, December was reasonably sunny. England and Wales averaged 55 hours, 118% of average but Scotland enjoyed even more at 145%. One exception was that west Wales had another duller than average month.

Winds

There were two named storms in December. Caroline gave a gust of 93mph at Fair Isle on the 7th. Dylan arrived in the very unsettled spell after Christmas and gave a gust of 81mph at Southampton on the 29th. 66mph was recorded on the following day at Needles (Isle of Wight) and at Capel Curig (Snowdonia).