MONTHLY CLIMATOLOGICAL SUMMARY FOR 12/2009

HEAT COOL

MEAN DEG DEG WIND SPEED DOM MEAN MEAN SNOW

DAY TEMP HIGH TIME LOW TIME DAYS DAYS RAIN AVG HI TIME DIR BAROM HUM COVER 9AM

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1 1.4 3.6 8:08pm -1.8 8:32am 14 0 2.00 4 32 7:21pm WSW1008.30 84

2 5.1 6.1 12:21pm 2.8 12:25am 12 0 1.00 4 34 12:13am SE997.15 97

3 5.2 6.3 11:07am 4.0 1:26pm 13 0 5.00 4 24 2:08pm W994.21 89

4 4.5 7.1 1:07pm 2.4 8:15am 13 0 0.00 4 24 1:57am W1003.43 71

5 6.6 9.2 11:58pm 4.6 12:00am 11 0 6.00 4 33 10:28pm SSE993.65 94

6 8.2 11.1 5:12am 5.8 9:27pm 10 0 8.00 4 30 2:05am NW988.08 89

7 7.0 9.1 4:07pm 5.0 3:00am 11 0 2.00 7 32 3:29pm SE993.20 86

8 6.0 8.6 11:12pm 2.8 8:04am 12 0 1.00 3 24 7:12pm SSE1004.67 93

9 8.2 9.4 4:11am 6.5 11:54pm 10 0 1.00 2 20 4:17am SSE1013.24 94

10 5.3 8.7 1:34pm 1.6 11:27pm 13 0 0.00 1 16 11:34am W1026.04 84

11 2.5 4.6 1:03pm 0.6 7:48am 16 0 0.00 0 10 2:29am WSW1034.96 95

12 4.8 6.7 1:25pm 3.6 12:00am 10 0 0.00 1 12 2:39pm WSW1036.22 96

13 4.7 5.9 12:27pm 2.6 10:17pm 13 0 0.00 3 17 9:00pm WSW1032.26 77

14 5.8 8.5 8:57pm 2.7 12:00am 9 0 2.00 6 26 5:51pm WSW1021.32 90

15 5.7 7.3 12:40am 4.9 9:40am 12 0 3.00 1 16 10:06pm WSW1018.79 85

16 5.5 6.5 4:50pm 3.7 11:57pm 12 0 8.00 5 24 12:33pm WSW1012.13 94

17 1.7 3.7 12:00am -0.8 11:12pm 16 0 5.00 6 36 1:56pm ESE1017.42 83 Dusting

18 -0.7 0.2 3:20am -2.0 10:49pm 19 0 0.00 0 0 12:00am N1020.86 72 3cm

19 -1.6 1.5 4:59pm -4.9 7:32am 20 0 0.00 1 15 2:08pm WNW1008.47 77 3cm

20 -2.2 1.0 9:10pm -6.4 4:06am 19 0 0.00 0 10 2:08pm S993.73 74 7cm

21 -0.2 1.1 11:03am -3.6 10:47pm 18 0 0.00 0 17 11:08am SE987.10 91 8cm

22 -3.7 3.4 11:50pm -6.8 8:56am 21 0 0.00 0 20 11:42pm NW981.90 95 7cm

23 0.0 3.4 12:00am -4.5 9:39pm 17 0 0.00 1 20 12:00am WNW986.74 81 5cm

24 -0.5 1.3 12:53pm -4.2 12:00am 18 0 0.00 0 8 6:30pm ESE988.67 93 10.5cm

25 -1.1 1.5 2:07pm -4.3 2:23am 18 0 0.00 0 14 2:47pm W994.92 90 8cm

26 1.3 3.0 12:44pm -1.3 8:23am 17 0 1.00 0 13 6:54pm SSE994.25 94 10cm

27 2.4 3.2 1:59pm 1.6 11:59pm 16 0 7.00 4 23 3:02pm W994.26 92 6cm

28 -0.6 1.6 12:00am -2.6 8:17pm 18 0 0.00 0 14 12:00am WSW1005.13 82 4cm

29 1.3 2.6 12:54pm -1.6 1:30am 16 0 2.00 2 21 3:43pm ESE1001.62 93 3cm

30 2.4 3.1 7:37am 1.0 11:25pm 14 0 1.00 10 38 2:52pm E1000.59 78 2cm

31 1.2 2.2 3:15am -0.8 11:55pm 17 0 1.00 4 23 12:00am ESE1006.26 83 2cm/partial cover >50%

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TOT 2.7 11.1 6/12/09 -6.8 22/12/09 456 0 56.00 3 38 30/12/09 ESE1004.76 87

Average Maximum Temperature : 4.9ºC (40.8ºF)
Average Minimum Temperature :  0.3ºC (32.5ºF)
Mean Temperature (Max+Min/2):  2.6ºC (36.7ºF)
 
High Temperature            : 11.1ºC (52.0ºF) 6th  
Low Temperature             : -6.8ºC (19.8ºF) 22nd 
 
Days above 20ºC             :  0 Days
Days below  0ºC             :  14 Days
 
Monthly Rainfall            :  56 mm
Rain Days >1mm              :  17 Days
 
Snow cover at 9am           :  15 Days
Maximum snow depth 9am      :  10.5cm 24th 
 
Maximum Wind Gust           :  38 mph 30th
 
Monthly Summary
 
A very cold month by the standards of this decade. Well below average, the mean temperature of 2.6ºC being a
hefty 1.6ºC colder than the 71-00 Durham mean of 4.2ºC, and 2.1ºC colder than the Newton Aycliffe 5 year 
rolling average of 4.7ºC – obviously this month will bring the 6 year rolling average down! The warmest day 
of 11.1ºC was the only day to reach double figures and it is also the coldest maximum temperature recorded in
any December at this station. The coldest minimum of -6.8ºC was also a cold record for this station. The 
rainfall total of 56mm was around average compared to the 71-00 Durham mean, but slightly more than the 
Newton Aycliffe 5 year rolling  average of 42.2mm. Another record to fall was air frosts – this is when the
temperature falls below 0ºC – this happened on 14 days. 
 
But perhaps the most remarkable or memorable event of December 2009 as well as the persistant cold, was snow. 
The Met Office definition of a lying snow day is a day where snow covers more than 50% of the ground at 9am 
in the morning. For record keeping purposes I use the same standard and starting on the 17th with a dusting 
of snow until the 31st when there was still frozen snow on the ground, albeit broken cover at 9am, December 
had 15 consecutive days of lying snow on the ground. This is also a record and it is unusual to say the least
for snow cover to last so long, especially considering the maximum recorded average depth was an unremarkable
10.5cm. A combination of persistant cold near or below 0ºC, and also the low strength of the December sun 
helped the snow stay around so long. I am convinced that had this snow fallen in February, even if the 
temperature was as low, that the snow would have melted fully on 2 or 3 occasions during the spell, because 
of the stronger sun. Certainly for longevity, the snow picked the best time to arrive, around the winter 
equinox. 
 
And let us not forget we had a proper white Christmas with good snow cover lying. Not only that but it
managed to snow on Christmas Eve and also on Christmas Day evening!
 
Certainly in 6 years of recording (72 full months) this month was a bit special and memorable, easily the
harshest winter month. I would personally put it near but not quite alongside the truly exceptional July 2006
which was memorable for different reasons, heat, drought and sunshine.