December 2019

The spectacular Triassic sandstone cliffs just east of Sidmouth basking in sunshine on a December day

A rather interesting month. Lots of sunshine and showers with many 'summer-like' thunderstorms at times leading to torrential downpours. Much calmer and drier during the final week. Mild throughout by day with only slight to moderate air frosts under clear, starry skies. A little warmer and sunnier than normal but with well-above average rainfall. Warmest December since 2018 (9.1C); sunniest since 2017 (91.4 hours) and the wettest since 2012 (171 mm).

Summary for December 2019
Mean Max: 10.9ºC (+1.6ºC)
Mean Min: 4.3ºC (+1.0ºC)
Mean: 7.6ºC (+1.2ºC)
High Max: 14.5ºC 6th
Low Max: 7.3ºC 2nd 
High Min: 10.2ºC 6th
Low Min: -1.8ºC 5th
Mean Grass Min: 1.6ºC  
Grass Min: -4.4ºC 18th
Days  >10°C 24 Days  
Days >5°C 31 Days  
Nights  >5°C 16 Days  
Nights  >0°C 24 Days  
Rain Total (gauge): 125.6 mm (140%)
Rain Total (tipping bucket): 123.5 mm (138%)
Rain Days >0.2 mm: 20 Days  
Rain Days >1.0 mm: 18 Days  
Max 24 hrs: 17.3 mm 19th
Days without any rain: 11  
Air Frost: 6 Days  
Grass Frost: 10 Days  
Snow Falling: 0 Days  
Snow (50%) @ 9am: 0 Days  
Ice Days: 0 Days  
Thunder Heard: 4 Days  
Hail <5 mm: 3 Days  
Hail >5 mm: 0 Days  
Fog @ 9am: 0 Days  
Total Monthly Sunshine: 87.5 Hours (110%)
Most Sunshine in a Day: 7.5 Hours 3rd 
Average Daily Sunshine: 2.8 Hours  
Sunless Days: 5 Days  
Cloudless Days: 1 Day 2nd
Total Possible Sunshine: 249.8 Hours  
Percentage of Total Sun: 35%  
Average Sunny Interval: 17.2 mins
Maximum UV Index: 1.3 2nd 
Mean Soil Temp @ 10 cm: 8.2ºC  
Min Soil Temp @ 10 cm: 6.6ºC 5th
Max Soil Temp @ 10 cm: 10.2ºC 29th
Mean Soil Temp @ 30 cm: 9.0ºC  
Min Soil Temp @ 30 cm: 7.5ºC 5th
Max Soil Temp @ 30 cm: 11.9ºC 29th
Mean Soil Temp @ 100 cm: 9.7ºC  
Min Soil Temp @ 100 cm: 9.2ºC 20th
Max Soil Temp @ 100 cm: 10.6ºC 1st
Ave 10 Min Wind >39 mph: 0.00 Days  
N: 2.45 Days 8%
NE: 0.91 Days 3%
E: 0.94 Days 3%
SE: 1.99 Days 6%
S: 6.57 Days 21%
SW: 5.57 Days 18%
W: 3.70 Days 12%
NW: 3.03 Days 10%
Calm: 5.84 Days 19%
Wind Chill Low: -4.4ºC 2nd 
Mean Wind: 4.6 mph  
Max Gust: 48 mph 10th
Mean Cloud Cover: 54%  
Mean RH @ 9am: 95%  
Rain >0.1mm/hour: 33.9 Hours  
Frost Duration: 32.8 Hours  
Air Frost in a Day: 9.8 Hours 2nd 
Mean Sea Temperature: 10.7ºC (+0.4ºC)
Normal for Month: 10.3ºC  
Max Sea Temperature: 12.1ºC 8th
Min Sea Temperature: 9.0ºC 3rd
Mean Pressure @ 9am: 1010.0 hPa  
Mean Pressure: 1008.7 hPa  
Max Pressure: 1035.7 hPa 28th
Min Pressure: 966.6 hPa 21st
Max Change in 24 hours: 31.5 hPa 9th
Radiation Daily Mean: 2.69 MJ/m²  
Max Daily Value: 3.96 MJ/m² 4th
Min Daily Value: 1.03 MJ/m² 19th
Number of Days with Data: 31 Days  
1-Hour Maximum: 269 W/m² 2nd 
Starting Time of the Hour:   12:00
Max Dewpoint: 12.3ºC 6th
Min Dewpoint: -3.6ºC 2nd 
Mean Dewpoint: 6.1ºC  
Max Humidity: 100% 4th
Min Humidity: 64% 9th
Mean Humidity: 91%  
 
Weather Data for Otter Valley, Devon. December 2019
  Temp oC Grass Hum (%) Soil oC (cm) Soil DP (oC) Wind (mph) Rain Air (hPa) W/m² UV Sun Frost Sea Observations
  Min Max Min Min Max 10 30 100 (cb) Min Max Max Ave Run mm Min Max Max Max Hours Hours Temp
1 2.5 8.6 1.1 79 96 8.7 9.4 10.6 4.0 1.4 5.4 21 5.4 130 0.0 1018 1029 262 1.1 5.3 0.0 11.1 Sunny intervals all day
2 -2.9 7.3 -2.8 78 99 7.6 8.8 10.6 3.9 -3.6 4.1 10 1.4 32 0.0 1029 1034 311 1.3 5.4 9.8 10.3 Sunny intervals all day
3 0.1 11.1 0.0 78 99 7.2 8.3 10.6 4.0 -0.8 7.7 9 0.8 19 0.0 1024 1033 236 1.3 7.5 0.0 9.7 Sunny all day
4 -0.8 10.3 -0.6 77 100 6.8 7.8 10.5 4.4 -1.4 7.9 8 1.5 37 0.0 1019 1023 279 1.1 5.4 8.5 9.8 Sunny intervals all day
5 -1.8 10.6 -1.1 88 100 6.6 7.5 10.0 4.4 -2.3 9.6 23 3.1 74 0.0 1016 1023 228 1.1 2.1 0.1 9.8 Sunny intervals all day
6 10.2 14.5 8.3 80 96 8.1 8.0 10.0 3.9 8.7 12.3 28 6.9 165 3.2 1005 1016 222 1.0 1.9 0.0 11.4 Sunny intervals all day
7 5.7 11.4 3.3 88 99 8.4 8.4 10.0 4.0 5.2 9.9 25 2.9 69 0.0 1010 1016 235 1.1 2.2 0.0 11.7 Sunny intervals all day
8 6.3 12.7 4.4 75 98 8.9 8.9 10.0 4.2 4.8 12.2 42 8.8 211 3.9 996 1010 292 1.1 3.6 0.0 12.0 Sunshine & thundery showers
9 7.6 11.0 0.0 64 96 8.5 8.9 10.0 6.9 -0.2 7.7 37 8.6 206 4.1 995 1026 228 1.1 6.6 0.0 11.5 Sunny intervals all day
10 -0.7 12.5 -0.6 88 100 8.1 8.9 10.0 4.9 -1.4 12.1 48 13.8 331 0.7 1004 1026 48 0.0 0.0 4.8 11.4 Cloudy all day
11 1.3 8.8 0.0 82 100 7.9 8.7 10.0 5.0 0.7 6.9 22 2.0 47 1.8 1002 1010 268 0.9 3.0 0.0 11.0 Sunny intervals all day
12 0.0 10.6 -0.6 93 100 7.5 8.3 10.0 5.0 -0.5 10.3 26 5.1 122 7.8 977 1006 115 0.8 0.3 0.0 11.2 Rain, intermittent all day
13 6.4 10.4 3.3 67 98 7.8 8.3 9.7 6.9 3.6 9.6 39 7.3 175 6.2 976 989 217 1.0 5.8 0.0 11.3 Sunny intervals all day
14 5.8 11.2 2.8 64 96 7.8 8.3 9.5 4.9 2.4 9.7 37 7.3 176 10.1 980 996 226 1.0 5.2 0.0 11.2 Sunny ints, thunderstorm pm
15 4.6 11.1 1.7 76 97 7.6 8.3 9.4 5.0 3.2 7.8 33 7.2 174 12.2 988 998 263 1.0 5.7 0.0 11.1 Sunny ints, thunderstorm pm
16 1.5 9.3 1.7 93 100 7.0 7.9 9.4 4.9 1.0 8.5 11 0.6 15 0.0 997 1001 244 1.0 1.7 0.0 9.9 Sunny intervals all day
17 1.7 8.0 -1.7 96 99 7.2 7.8 9.4 4.0 0.1 7.7 5 0.3 7 2.8 997 1005 219 0.8 2.4 0.0 10.1 Sunny intervals all day
18 -1.5 11.9 -4.4 87 100 6.8 7.7 9.4 4.6 -1.9 11.1 35 7.0 168 12.9 998 1008 132 0.8 0.2 8.4 10.5 Brief sunny intervals all day
19 9.3 12.2 7.8 93 98 8.3 8.1 9.4 5.4 8.2 11.8 35 11.0 263 17.3 986 998 56 0.7 0.0 0.0 10.9 Rain all day, thunder pm
20 6.6 11.0 -1.1 89 99 8.6 8.8 9.2 5.0 1.8 10.2 28 3.4 82 5.3 978 986 213 0.9 1.5 0.0 10.3 Sunshine & showers
21 3.5 10.8 -0.6 91 100 7.8 8.9 9.4 4.5 3.1 10.3 31 4.0 97 10.6 967 983 280 0.9 0.6 0.0 10.5 Sunny intervals all day
22 6.6 11.4 1.7 81 99 7.9 9.1 9.4 4.5 5.8 8.7 21 4.0 97 3.0 969 997 246 0.9 3.8 0.0 10.6 Sunny intervals all day
23 6.6 12.6 2.8 78 97 8.0 9.4 9.4 4.0 5.9 9.0 21 3.9 93 2.8 997 1013 275 1.0 3.6 0.0 10.8 Sunny intervals all day
24 6.3 12.4 0.6 85 99 8.3 9.5 9.4 4.0 5.5 10.3 26 5.5 131 1.6 1006 1016 220 1.0 2.6 0.0 10.8 Sunny intervals all day
25 -0.2 9.3 -3.3 82 99 7.6 9.1 9.4 4.0 -0.6 7.5 26 2.4 58 0.0 1016 1026 229 1.0 6.0 1.1 10.5 Sunny intervals all day
26 9.1 12.6 6.1 81 98 8.3 9.5 9.4 4.7 6.8 12.0 38 7.6 183 11.5 1006 1021 226 0.9 0.5 0.0 10.6 Rain am, sunny ints pm
27 9.8 12.7 8.9 95 99 9.6 10.4 9.4 6.6 9.3 12.1 22 1.1 27 5.5 1018 1033 117 0.8 0.0 0.0 10.6 Cloudy all day
28 7.2 11.5 2.8 91 99 10.0 11.3 9.4 4.2 6.7 10.7 14 2.2 49 0.2 1033 1036 101 0.8 0.0 0.0 10.6 Cloudy all day
29 9.1 10.4 6.7 90 97 10.2 11.9 9.4 4.7 7.7 9.3 21 4.3 108 0.0 1031 1035 147 0.9 0.2 0.0 10.4 Sunny intervals all day
30 4.3 11.2 0.0 92 99 10.1 11.6 9.4 4.0 3.3 10.1 12 1.4 50 0.0 1028 1031 220 1.0 4.3 0.0 10.2 Cloudy all day
31 5.5 8.9 2.2 90 94 10.0 11.6 9.4 4.0 5.6 7.9 10 1.7 17 0.0 1029 1031 89 0.8 0.0 0.0 10.4 Cloudy all day
4.2 10.9 1.6 84 98 8.2 9.0 9.7 4.7 2.8 9.4 25 4.6 3411 123.5 1003 1015 208 0.9 87.5 32.8 10.7  
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