It was a mild and sunny December in Royston, with above average rainfall.

After the very dry Spring and Autumn seasons in 2011 it appeared at the end of November that the year might be the driest since 1921 provided the December rainfall was average or below. In the event rainfall in December was above average to scupper the potential record by the narrow margin of 6.8 millimetres, and it was the driest year since 1996 only.

Total rainfall in December was 60.4 millimetres, which is 120% of the 30 Year (1981/2010) average. The number of "rain days" (0.2 millimetres or more) in the month was 21, with rainfall exceeding 1.0 millimetre on 14 of these days. The wettest day of the month was 12^th with rainfall of 10.0 millimetres. It was the wettest December since 2009 only.

Snow was not a feature of this generally mild month although Royston received a covering of snow on the morning of 16^th, but this had mostly thawed by the end of the day. The only other day in December snow was observed to fall was on 18^th but this snow was insufficient to settle.

In complete contrast to the severe December last year, temperatures were above average this month and it was the mildest December since 2006. The Christmas period was notably mild and the highest temperature of the month, 13.7°C, occurred on 26^th. This made it the mildest Boxing Day on record (1972). The mildest Christmas day on record was in 1974, the maximum temperature of 12.0°C on 25^th this year falling short of this record by 1.1°C.

The lowest temperature recorded in December was –1.7°C on 18^th, this being the highest absolute minimum temperature in December since 2002. The lowest grass minimum temperature in the month was –4.2°C on 19^th. Totals of 3 air frosts and 9 ground frosts occurred in December. This was the lowest number of air frosts in December since 1997, and compares with 22 in December last year!

The mean daily maximum temperature in December was 8.7°C, which is 1.7°C above the 30 Year (1981/2010) average. The mean night minimum temperature of 4.0°C was 1.1°C above average.

The lowest day maximum temperature in the month was 2.9°C on 16^th whilst the highest night minimum temperature was 10.9°C on 26^th.

The mean earth temperature at 30 cms depth as measured at 0900 GMT daily was 6.0°C, peaking at 8.3°C on 1^st and falling to its lowest value of 3.8°C on 19^th.

December was a month of two halves as far as sunshine is concerned. Sunshine in the period 1^st/15^th totalled 53.0 hours, but the equivalent figure for the period 16^th/31^st was only 21.7 hours. This gave a sunshine total for the month of 74.7 hours, which is 157% of the 1971/2000 average. This percentage reduces to 106% when the December sunshine is compared with the average of the last 13 years, indicating a substantial increase in December sunshine in recent years.

The sunniest day of the month was 22^nd with 6.6 hours sunshine. Only 3 days (11^th, 19^th and 21^st) in December were completely sunless. It was the sunniest December since 2009 only.

With a mean wind speed of 10.6 mph December was the windiest month of the year. A total of 17 days experienced wind gusts of 30 mph or more, and the maximum wind gust speed recorded was 49 mph on 13^th. The windiest day was 13^th with a mean wind speed of 15.7 mph, whilst the calmest day was 1^st with a mean wind speed of 6.1 mph.

Wind directions as observed at 0900 GMT daily had a westerly component on all but 2 days in the month, per the following analysis: NORTH 0 days, NE 0, E 0, SE 0, S 2, SW 19, W 9, NW 1 and CALM 0.

The mean MSL air pressure in December was 1010.2 mB, which is 4.6 mB below the 1981/2010 average. The highest pressure value recorded was 1033.8 mB on 27^th and the lowest such reading was 980.6 mB on 16^th.

The mean relative humidity in December was 85.6%. The highest daily (00/00) mean relative humidity was 96.1% on 21^st and the lowest daily mean relative humidity was 75.2% on 7^th. The absolute lowest relative humidity reading in the month was 59% at 1350 GMT on 7^th.

Fog (visibility < 1000 metres @ 0900 GMT) was observed on 2 days (16^th and 21^st) in December.

Year 2011: Despite a cooler than average Summer it was nonetheless the warmest year in Royston since at least 1972 due mainly to the very mild Spring and Autumn seasons, the annual mean temperature exceeding the previous warmest year of 2006 by just 0.2°C. It was the driest year since 1996 and the sunniest year since 2009 only. The mean daily maximum temperature in 2011 was 15.8°C, which is 1.5°C above the 1981/2010 average. The mean night minimum temperature was 0.9°C above average at 7.9°C. Total rainfall in 2011 was 409.9 millimetres, which is 68% of the 1981/2010 average. Sunshine was 16% above the 1971/2000 average at 1742.1 hours.

Met. Observer, Royston (Iceni) Weather Station

7^th January 2012