The month began where November finished with a flow of warm, moist air from the Atlantic. This resulted in maxima well above average, sometimes occurring at night, as the weather fronts crossed the area. It was also a very wet period with substantial falls on several days, 14.6mm on the 1st made it the wettest day for almost a month.
The second week was very little different with a south-westerly airflow producing temperatures well above average, except for a light frost early on the 13th under clear skies. The rainfall amounts were, however, minimal compared to the first week.
Interestingly, the depth of water in the River Kennet at Winterborne Monkton, close to where the springs rise for the start of the river, started to flow on December 1st before stopping on the 4th at 16.15 when the gauge indicated no depth of water. The gauge then indicated that a flow of water began again on the 5th December at 07.15 and has continued to indicate a level since that time although variable, the highest of 0.19m was logged on the 6th at 04.45. The highs and lows obviously correlate with the wet spells this month. During the drier second week the water level once again fell to zero, logged on the 11th at 23.30.
The unsettled weather that brought the warm moist air continued until just before Christmas. A minor depression formed off the coast of Brittany on the 21st that produced a significant shift in wind direction. For almost the whole month, so far, we have had an air flow from a south-westerly quadrant. Initially, the wind from the east, usually a cold direction, brought the air mass from the eastern Atlantic, with day and night temperatures still above average.
There was a significant change in our weather pattern on the 23rd. The recent depression had begun to head towards the Mediterranean allowing a high-pressure system, that had been building over Scandinavia, to edge over the UK. This resulted in the wind backing further, into the northeast, and that began a flow of much cooler and drier air. There was also a considerable pressure gradient between the two systems that resulted in the wind strength increasing, a maximum gust of 30mph was logged on the 25th. However, this flow of strong, cold air produced a wind chill, which meant outside it felt much colder than that indicated on thermometer.
Up to and including the 22nd every daily maximum temperature was above average, whilst 17 of the minima in December were above average. Up to and including the 23rd, the average maximum was 2.9C above average and the average minimum was 2.6C above average.
The month ended with a mainly gloomy, dull, dry and cool week as maximum temperatures dropped below average due to a persistent northeasterly breeze with little sunshine. On the 30th the wind began to back into the north heralding a much colder period of Arctic air streaming down from the north.
The coldest night of the month occurred in the early hours of the 31st with a minimum of -3.8C.
December had a mean temperature 1.2C above my long-term average whilst the rainfall of 124.4mm was 134% of my 42-year record or + 31.3mm.
Interesting facts for 2025:
| Coldest Night: -7.5C on 11th January | Coldest Day: 0.8C on 4th & 8th January |
| Hottest Day: 32.9C on 11th July | Hottest Night: 18.5C on 1st July |
| Heatwave: 3 consecutive days equal to or above 27C for Wiltshire: 9th – 13th July | |
| Wettest Day: 25.7mm on 14th November | |
| Longest dry period: 14 days 12th – 25th August | |
| Warmest soil temperature at a depth of 5cm: 27.0C on 12th July | |
| Air Frosts: 40 | |
| Highest Solar: 1257 W/m2 on 29th June | |
| Highest Barometric Pressure: 1044.7mb on 6th February | |
| Lowest Barometric Pressure: 971.0mb on 6th January |
Hilda Moore BEM: awarded for ‘Tennis Coaching and Volunteering’, but also as recognition of her role for sport in Marlborough
