December 2010
Snow on the beach on Xmas Day 2010, a rare sight here on the south coast of Devon.
Snow on the beach on Xmas Day 2010, a rare sight here on the south coast of Devon.
Summary for  December 2010
Mean Max: 3.7ºC (-5.4ºC)
Mean Min: -2.3ºC (-5.8ºC)
Mean: 0.7ºC (-5.6ºC)
     
High Max: 10.6ºC 28th
Low Max: -1.4ºC 25th
High Min: 8.1ºC 29th
Low Min: -11.6ºC 26th
Mean Grass Min: -3.8ºC  
Grass Min: -12.0ºC 7th
     
Rain Total (gauge): 31.6 mm (33%)
Rain Total (tipping bucket): 20.7 mm (21%)
Rain Days >0.2 mm: 10 Days  
Rain Days >1.0 mm: 5 Days  
Max 24 hrs: 9.5 mm 27th
Days without any rain: 21  
     
Air Frost: 21 Days  
Ground Frost: 25 Days  
Snow Falling: 2 Days  
Snow (50%) @ 9am: 10 Days  
Thunder Heard: 0 Days  
Hail <5 mm: 0 Days  
Hail >5 mm: 0 Days  
Fog @ 9am: 3 Days  
     
Total Monthly Sunshine: 91h:27m  
Total Monthly Sunshine: 91.4 Hours  
Most Sunshine in a Day: 07h:23m 6th
Average Daily Sunshine: 02h:57m  
Sunless Days: 9 Days  
Cloudless Days: 10 Days  
Total Possible Sunshine: 249h:24m  
Percentage of Total Sun: 37%  
     
Mean Soil Temp @ 30 cm: 2.6ºC  
Min Soil Temp @ 30 cm: 1.4ºC 27th
Max Soil Temp @ 30 cm: 4.2ºC 30th
Mean Soil Temp @ 100 cm: 5.5ºC  
Min Soil Temp @ 100 cm: 4.2ºC 29th
Max Soil Temp @ 100 cm: 7.8ºC 1st
     
Mean 10 Min Wind >39 mph: 0.00 Days  
N: 7.98 Days  
NE: 5.55 Days  
E: 2.63 Days  
SE: 2.67 Days  
S: 0.67 Days  
SW: 0.71 Days  
W: 3.33 Days  
NW: 4.95 Days  
Calm: 2.52 Days  
Mean Wind: 3.6 mph  
Max Gust: 38 mph 16th
     
Mean Cloud Cover: 75%  
Mean RH @ 9am: 87%  
Rain Duration >0.1mm/hour: 18.0 Hours  
Frost Duration: 372.5 Hours  
Max Frost Duration in a Day: 24.0 Hours 7th
     
Mean Sea Temperature: 7.2ºC  
Normal for Month:    
Max Sea Temperature: 9.4ºC 1st
Min Sea Temperature: 5.4ºC 27th
     
Mean Pressure @ 9am: 1014.6 hPa (-0.0 hPa)
Mean Pressure: 1014.8 hPa (+0.2 hPa)
Max Pressure: 1039.0 hPa 15th
Min Pressure: 990.5 hPa 18th
     
Max Dewpoint: 9.1ºC 28th
Min Dewpoint: -14.3ºC 26th
Mean Dewpoint: -2.3ºC  
     
Max Humidity: 93% 28th
Min Humidity: 63% 1st
Mean Humidity: 85% (-2)

 

An extremely cold month throughout with frequent, severe frosts and 10 days of snow lying.

Temperatures stayed well below average until the last 5 days of the month. Frosts were persistent and frequent with 3 days when the temperature failed to get above freezing (ice-days). There was 30 cm of level snow lying on the 20th.
Precipitation was well below average with only 33% of the normal expected.
Frosts were frequent and severe, on the 26th the temperature went down to -11.6°C, this is the coldest temperature I have ever recorded.
Sunshine amounts were generally above normal though there were 5 consecutively cloudy days at the end of the month, this is the longest 'dullest' period recorded for any month.
Soil temperatures were well below normal through.
Winds were dominant from a northerly direction with a near-complete absence of southerly or south-westerly winds.
Rainfall duration was only 18 hours and reflected in what was a very dry month overall.
Sea temperatures fell sharply throughout the month and ended up being extremely below average and almost historically cold.
Mean pressure was around average.
Dewpoints were well below average.
The RH ended up being a little below normal due to large incursions of very dry, cold Arctic air.
Weather Data for Otter Valley, Devon.  December 2010  
  Temp (oC) Hum (RH%) Dewpoint (oC) Wind (mph) Rain Pressure (hPa) Grass Sun  
  Min Max Ave Min Max Ave Min Max Ave Max Ave Run mm Min Max Ave Min Hours Observations
1 -2.9 0.1 -1.4 63 81 72 -7.8 -3.8 -5.8 28 9.5 226 0.0 1008 1011 1009 -5.9 0.0 Cloudy all day
2 -2.4 0.7 -0.9 73 87 80 -6.1 -2.9 -4.5 22 7.8 186 0.9 1007 1011 1009 -4.8 0.3 Brief sunny intervals all day
3 -9.1 4.1 -2.5 77 89 83 -11.7 0.9 -5.4 15 2.5 60 0.0 1007 1015 1011 0.0 5.1 Sunny intervals all day
4 -0.9 5.8 2.5 88 92 90 -2.9 4.0 0.6 23 1.1 27 2.2 1002 1007 1004 0.3 0.0 Rain, intermittent all day
5 -1.2 4.3 1.6 90 92 91 -4.3 2.6 -0.9 7 0.3 6 0.0 1004 1006 1005 -7.9 4.5 Foggy am, sunny pm
6 -3.2 0.7 -1.3 89 92 91 -8.6 -0.8 -4.7 11 1.7 41 0.0 1001 1004 1002 -10.8 7.4 Sunny all day
7 -9.3 -0.8 -5.1 88 91 90 -11.2 -2.4 -6.8 16 2.1 50 0.0 1003 1007 1005 -12.0 6.5 Sunny all day
8 -3.2 1.9 -0.7 72 91 82 -6.4 -2.1 -4.3 22 5.9 141 0.0 1007 1024 1015 -8.5 4.7 Sunny intervals all day
9 -8.4 4.3 -2.1 82 91 87 -10.8 1.9 -4.5 7 0.6 14 0.0 1024 1035 1029 -10.8 6.5 Sunny all day
10 0.2 6.8 3.5 83 92 88 -5.6 4.4 -0.6 18 1.8 44 0.0 1032 1035 1033 -7.2 0.3 Brief sunny intervals all day
11 4.3 6.8 5.6 82 88 85 1.6 3.9 2.8 22 4.1 98 0.0 1024 1032 1028 0.9 0.0 Cloudy all day
12 1.8 6.6 4.2 75 89 82 -3.9 2.7 -0.6 14 2.4 58 0.0 1022 1025 1024 -6.3 7.0 Sunny all day
13 -1.3 4.9 1.8 81 91 86 -5.6 2.3 -1.7 11 1.8 42 0.0 1025 1029 1027 -7.5 6.5 Sunny all day
14 -4.3 5.0 0.4 82 91 87 -6.5 1.9 -2.3 12 2.4 58 0.0 1029 1036 1033 -7.9 5.6 Sunny all day
15 0.3 6.0 3.2 77 91 84 -2.6 2.1 -0.3 14 2.7 65 0.0 1033 1039 1036 -5.5 6.9 Sunny all day
16 3.0 7.7 5.4 73 90 82 -2.7 5.2 1.3 38 8.3 199 3.5 1005 1033 1019 -1.5 0.0 Cloudy am, rain pm
17 -4.7 1.4 -1.7 77 89 83 -7.6 -0.8 -4.2 22 2.6 62 1.3 997 1006 1002 -8.8 2.0 Heavy snow showers
18 -3.7 0.8 -1.5 86 91 89 -11.0 -0.9 -6.0 6 0.5 13 0.0 991 997 994 -2.6 6.2 Sunny all day
19 -11.0 -0.9 -6.0 82 90 86 -13.2 -3.5 -8.4 23 4.2 101 0.0 991 998 994 -2.8 0.7 Brief sunny ints pm
20 -5.3 1.8 -1.8 83 90 87 -7.7 0.0 -3.9 17 5.2 136 0.2 997 999 998 -9.6 2.6 Sunny ints after early snow
21 -1.7 0.8 -0.5 85 91 88 -5.4 -1.5 -3.5 9 1.9 47 0.2 998 1005 1002 -0.8 3.0 Sunny am, cloudy pm
22 -5.5 0.3 -2.6 84 90 87 -7.5 -2.1 -4.8 23 4.6 110 0.0 1005 1009 1007 -1.4 0.4 Brief sunny ints am
23 -2.2 0.8 -0.7 75 87 81 -4.9 -3.0 -4.0 24 9.4 225 0.0 1009 1016 1012 -1.2 0.6 Brief sunny ints am
24 -5.2 1.8 -1.7 74 87 81 -8.4 -2.5 -5.5 19 4.5 100 0.0 1016 1024 1020 -1.4 5.5 Sunny all day
25 -9.4 -1.4 -5.4 83 89 86 -11.9 -3.4 -7.7 6 0.7 16 0.0 1024 1031 1028 -2.9 7.1 Sunny all day
26 -11.6 3.3 -4.3 74 91 83 -14.3 -0.3 -7.3 20 1.8 43 0.0 1021 1032 1026 -3.9 1.7 Sunny intervals all day
27 3.6 5.5 4.6 70 91 81 -1.3 3.0 0.9 24 9.1 218 9.5 1009 1021 1015 -0.3 0.0 Cloudy all day
28 6.2 10.6 8.4 91 93 92 3.2 9.1 6.2 20 3.0 73 2.2 1008 1015 1011 -0.3 0.0 Cloudy all day
29 8.1 10.1 9.1 93 93 93 6.4 8.5 7.5 10 1.5 36 0.4 1015 1019 1017 5.5 0.0 Cloudy all day
30 4.8 8.8 6.8 89 93 91 3.2 7.2 5.2 18 4.2 100 0.2 1019 1023 1021 7.1 0.0 Cloudy all day
31 4.2 6.3 5.3 84 89 87 1.8 4.1 3.0 15 3.6 88 0.0 1023 1026 1025 2.4 0.0 Cloudy all day
-2.3 3.7 0.7 81 90 85 -5.6 1.1 -2.3 17 3.6 2681 20.7 1011 1018 1015 -3.9 91.37  

Graphs for December 2010
Figure 1. Temperature and Rainfall for December 2010.
Figure 2. Sunshine, air pressure and mean wind speed for December 2010.
Figure 3. Wind direction for December 2010.
Figure 4. Soil & sea surface temperature (SST) for Lyme Bay for December 2010.
Figure 5. Wind run, maximum gusts and mean pressure for December 2010.