December 2008

Temperatures
(all temperatures in degrees Celsius; all averages 1961 – 1990)

Mean daily maximum: 6.4
Difference from average: -0.2

Mean daily minimum: 0.6
Difference from average: -0.5

Mean air temperature: 3.6
Difference from average: -0.3

Absolute maximum: 12.3 (21st)

Absolute minimum: -4.4 (1st)

Mean grass minimum: -2.3

Absolute grass minimum: -11.2 (1st)

Number of ground frosts: 21

Number of air frosts: 12

Mean soil temperature at 30cm depth: 4.6

Mean soil temperature at 100cm depth: 7.3

Rainfall
(all totals in millimetres; all averages 1961 – 1990)

Total for the month: 57.0
Difference from average: -0.4

Percentage of the average: 99%

Wettest day: 13.2 (13th)

Number of rain days (>0.25mm): 12

Number of wet days (=>1mm): –

3-month total rainfall to 31st December: 155.5
Difference from average: -16.5

6-month rainfall total to 31st December: 489.5
Difference from average: 143.3

12-month rainfall total to 31st December: 817.1
Difference from average: 168.1

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 90%

Sunshine
(all averages 1961 – 1990)

Total for the month: 72.3 hours
Difference from average: 26.7

Percentage of the average: 159%

Mean daily sunshine: 2.3 hours
Difference from average: 0.8

Sunniest Day: 7.0 hours (9th)

Number of days with no recorded sunshine: 2

Cumulative total sunshine since 1st January: 1352 hours
Difference from average: 22.8

Wind

The mean wind speed: 11.7km/h [6.3kt]
Difference from average: -3.6km/hr

The highest gust: 86.5km\h [46.7kt] from 233° at 21:14 GMT on 19th

ISSN1350-483

Comments on December 2008
This was the coldest December since 2001. It was the second time in three months that monthly mean air temperature was below average; October was the first month since March 2006 when mean air temperature was below average. It was notably cold on the 31st with a maximum below zero (-0.3°C). There was the highest number of ground frosts in December since 2001. The lowest grass minimum since 1995 was recorded on the 1st, continuing the very cold end to November. Rainfall was just about average for the month, but the 6- and 12- month totals remained well above average. It was nevertheless a very sunny month, the 7th sunniest December on record. Even so, this December total has been exceeded in 2003, 2004 and 2006.

2008 was the equal coldest year (with 2001) since 1996 (9.3°C). The 12-month average (9.25 to two decimal places) is the lowest since October 2001. Even so, it was still the 19th warmest year since 1850! It was a wet year, the wettest year since 2000 with the most rain days since 2002. The total sunshine was a just little above average.

Professor Tim Burt
Department of Geography
Durham University