December 2012

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

Mean daily maximum: 6.7
Difference from average: +0.1

Mean daily minimum: 1.1
Difference from average: 0

Mean air temperature: 3.9
Difference from average: 0

Absolute maximum: 12.1 (29th)

Absolute minimum: -4.7 (13th)

Mean grass minimum: -1.5

Absolute grass minimum: -8.1 (13th)

Number of ground frosts: 22

Number of air frosts: 9

Mean soil temperature at 30cm depth: 4.9

Mean soil temperature at 100cm depth: 7.4

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

Total for the month: 99.8
Difference from average: +33.4

Percentage of the average: 174%

Wettest day: 26.8 (20th)

Number of rain days (>0.25mm): 21

Number of wet days (=> 1mm): 16

3-month total rainfall to 31st December: 307.6
Difference from average: +135.6

6-month rainfall total to 31st December: 631.4
Difference from average: +285.2

12-month rainfall total to 31st December: 1033
Difference from average: +384

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 91%

Sunshine
(all averages 1961 – 1990)

Total for the month: 72.4 hours
Difference from average: +26.8

Percentage of the average: 159%

Mean daily sunshine: 2.3 hours
Difference from average: +0.8

Sunniest day: 7.3 hours (9th)

Number of days with no recorded sunshine: 2

Cumulative total sunshine since 1st January: 1246.4 hours
Difference from average: -82.8

ISSN1350-483

Comments on December 2012
All the focus was on rainfall: would another above-average month lead to a calendar-year total at Durham over 1000mm (40 inches) for the first time since records began in 1850? The answer was “yes”, with the total of 99.8mm more than enough to reach 1033mm for the year. It was the wettest December since 1978, the 16th wettest since 1850. Of course, all the long-period totals stayed well above average: it was the 36th highest of any 3-month total, the 3rd highest 6-month total (only beaten by two other 3-month totals in 2012) and the wettest ever 12-month period (beating the previous record, the 12 months up to and including February 2001, the only other time a 12-month total has exceeded 1000 mm at Durham, 1005.8mm). Not surprisingly, it was also the highest 9-month period on record, easily the wettest ever “end” to a calendar year at Durham. Recalling that the 3-month total to the end of March 2012 was the 39th lowest for any consecutive 3 months since 1850 (n = 1945), 2013 has been truly been an extreme year in terms of rainfall totals, from near-record drought to record deluge!

Mean air temperature was exactly average for December. It was less mild than last year but warmer than 2009 and 2010. There was a relatively high number of ground frosts (22) but a relatively small number of air frosts (9), mostly in the first half of the month. Despite all the rain, sunshine hours were above average, the sunniest December since 2004 (equal to 2006).

Professor Tim Burt
Department of Geography
Durham University