December 2019

Temperatures
(all temperatures in degrees Celsius; all averages 1981 – 2010)

Mean daily maximum: 8.0
Difference from average: +1.2

Mean daily minimum: 2.8
Difference from average: +1.7

Mean air temperature: 5.4
Difference from average: +1.5

Absolute maximum: 12.4 (5th, 6th)

Absolute minimum: -2.6 (1st)

Mean grass minimum: 1.2

Absolute grass minimum: -4.4 (31st)

Mean concrete minimum: 1.2

Absolute concrete minimum: -2.9 (18th)

Number of ground frosts: 12

Number of air frosts: 7

Mean soil temperature at 30cm depth:

Mean soil temperature at 100cm depth:

Rainfall
(all totals in millimetres; all averages 1981 – 2010)

Total for the month: 32.8
Difference from average: -26.3

Percentage of the average: 56%

Wettest day: 6.0 (18th)

Number of rain days (>0.2mm): 19

Number of wet days (=>1.0mm): 8

3-month total rainfall to 31st December: 227.8
Difference from average: +55.8

6-month rainfall total to 31st December: 463.4
Difference from average: +117.2

12-month rainfall total to 31st December: 735
Difference from average: +86

Sunshine
(all averages 1981 – 2010)

Total for the month: 61.9 hours
Difference from average: +10.1

Percentage of the average: 119%

Mean daily sunshine: 2.0 hours
Difference from average: +0.3

Sunniest day: 6.2 hours (3rd)

Number of days with no recorded sunshine: 4

Cumulative total sunshine since 1st January: 1213.9 hours
Difference from average: -164

Wind
(all data from West Building roof, Lower Mountjoy)

Average wind speed: 4.9kph

Maximum gust: 69.2kph (16:30, 5th, W)

ISSN1350-483

Comments on December 2019
Like the previous year, December temperatures were well above average. Mean air temperature was the equal 23rd highest since 1850, just 0.1°C below the 2018 value. Despite being a dry month, the mean minimum temperature was rather more above average than the mean maximum. Frequent cloud cover clearly helped to maintain night-time temperatures; usually dry winter months have cold, clear nights.

For the 4th year in row, December rainfall was below average, in this case the 36th driest December at Durham since 1850. Nevertheless, there were 19 rain days, an indication of the cloudy maritime air masses that dominated the month. The previous six months were all above average, so long-term accumulations remain well above average.

Sunshine was only a little above average, but even so, it was still the 24th highest sunshine total for December since 1882.

A warm December helped contribute to the 9th warmest year on record at Durham since 1850 (9.77°C). Other than 1949, all the warmer years have been this century. Not surprisingly, given the very wet summer and autumn, it was a wet year, but only the 45th highest on record: winter and spring were dry, so the annual total of 735mm was not exceptional. Overall, it was a poor year for hours of bright sunshine, the 25th dullest year on record at Durham since 1882. Another warm, wet and dull year!

Emeritus Professor Tim Burt
Department of Geography
Durham University