May 2011

A Dartmoor Tor on a breezy and cool May day.
A Dartmoor Tor on a breezy and cool May day.

Summary for  May 2011
Mean Max: 17.4C (+1.4C)
Mean Min: 8.0C (+0.7C)
Mean: 12.7C (+1.0C)
     
High Max: 20.9C 6th
Low Max: 14.8C 4th
High Min: 13.3C 30th
Low Min: 3.1C 13th
Mean Grass Min: 5.6C  
Grass Min: 1.7C 25th
     
Rain Total (gauge): 42.4 mm (75%)
Rain Total (tipping bucket): 39.8 mm (70%)
Rain Days >0.2 mm: 10 Days  
Rain Days >1.0 mm: 7 Days  
Max 24 hrs: 11.2 mm 8th
Days without any rain: 21  
     
Air Frost: 0 Days  
Ground Frost: 0 Days  
Snow Falling: 0 Days  
Snow (50%) @ 9am: 0 Days  
Thunder Heard: 3 Days  
Hail <5 mm: 0 Days  
Hail >5 mm: 0 Days  
Fog @ 9am: 0 Days  
     
Total Monthly Sunshine: 172h:33m  
Total Monthly Sunshine: 172.6 Hours (88%)
Most Sunshine in a Day: 12.8 27th
Average Daily Sunshine: 05h:34m  
Sunless Days: 1 Days  
Cloudless Days: 7 Days  
Total Possible Sunshine: 480h:58m  
Percentage of Total Sun: 36%  
Maximum UV Index: 9 29th
Average Daily UV Index: 6.5  
     
Mean Soil Temp @ 30 cm: 14.8C  
Min Soil Temp @ 30 cm: 14.0C 5th
Max Soil Temp @ 30 cm: 15.6C 11th
Mean Soil Temp @ 100 cm: 14.9C  
Min Soil Temp @ 100 cm: 14.6C 4th
Max Soil Temp @ 100 cm: 15.1C 21st
     
Mean 10 Min Wind >39 mph: 0.00 Days  
N: 0.33 Days  
NE: 2.03 Days  
E: 2.58 Days  
SE: 4.90 Days  
S: 4.09 Days  
SW: 3.74 Days  
W: 8.41 Days  
NW: 3.31 Days  
Calm: 1.60 Days  
Wind Chill Low: 2.3C 25th
Mean Wind: 5.9 mph  
Max Gust: 34 mph 23rd 
     
Mean Cloud Cover: 58%  
Mean RH @ 9am: 81%  
Rain Duration >0.1mm/hour: 16.8 Hours  
Frost Duration: 0.0 Hours  
Max Frost Duration in a Day: 0.0 Hours 1st
     
Mean Sea Temperature: 12.8C  
Normal for Month:    
Max Sea Temperature: 13.9C 11th
Min Sea Temperature: 11.6C 2nd 
     
Mean Pressure @ 9am: 1017.8 hPa (+2.0 hPa)
Mean Pressure: 1017.3 hPa (+1.5 hPa)
Max Pressure: 1028.9 hPa 25th
Min Pressure: 1004.6 hPa 1st
     
Max Dewpoint: 13.7C 7th
Min Dewpoint: -0.6C 25th
Mean Dewpoint: 7.0C  
     
Max Humidity: 92% 8th
Min Humidity: 41% 3rd 
Mean Humidity: 72% (-5)

 

After a stunningly sunny, warm and dry April, this month was more 'normal'.

Despite a generally breezy and often cloudy month, May ended up warmer and drier than average. There were no warm days (>21C) which has never happened before in the station record as May normally would have quite a few 'hot' days.

Rainfall was below the average and continued the dry theme of Spring 2011.
As would be expected in May, there were no air or grass frosts. Thunderstorms made a welcome return after a very long, unthundery period.
Sunshine levels were below the long term average of around 200 hours. This was the dullest May since 2007. UV levels were exceptionally high towards the end of May.
Soil temperatures were above normal at the beginning of the month and continued this way right through.
Winds were dominant from the west to north-westerly directions and the mean wind speed of 5.9 mph is very high for May. It was the windiest month since March 2008.
Rainfall duration was only 16.8 hours due to it falling in short, sharp periods from thunderstorms.
Sea surface temperatures were above normal at the beginning of the month but generally fell back to normal at the end.
Mean pressure was a little above the average for May.
Dewpoints were rather below average.
The RH ended up being well below normal due to regular incursions of dry air.
Weather Data for Otter Valley, Devon.  May 2011  
  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 10.6 19.6 15.1 57 82 70 6.4 11.6 9.0 24 8.1 192 0.0 1005 1007 1006 8.3 1.7 Brief sunny intervals all day
2 9.1 15.2 12.2 51 84 68 3.1 8.1 5.6 24 7.0 168 10.3 1007 1010 1008 8.3 1.5 Brief sunny intervals all day
3 5.0 16.4 10.7 41 83 62 0.4 6.3 3.4 23 7.4 177 0.0 1010 1017 1013 2.8 12.0 Sunny intervals all day
4 5.3 14.8 10.1 48 78 63 -0.5 6.6 3.1 23 5.6 135 0.0 1017 1019 1018 3.0 2.6 Brief sunny intervals all day
5 8.4 17.1 12.8 61 86 74 3.0 12.1 7.6 18 5.2 125 0.7 1015 1019 1017 6.0 4.8 Sunny ints all day
6 10.2 20.9 15.6 51 89 70 6.3 13.1 9.7 22 3.8 91 2.2 1011 1015 1013 7.5 3.2 Sunny ints, thunder evening
7 12.6 17.6 15.1 76 90 83 9.3 13.7 11.5 28 6.7 162 8.8 1006 1011 1009 9.9 0.2 Sunny, thunder evening
8 11.4 18.5 15.0 60 92 76 8.3 12.0 10.2 30 9.8 236 11.2 1005 1015 1010 9.2 11.2 Sunny intervals all day
9 10.7 18.5 14.6 66 91 79 7.7 12.0 9.9 28 8.7 210 0.0 1015 1020 1018 9.2 6.4 Sunny intervals all day
10 9.4 19.7 14.6 54 92 73 6.7 12.0 9.4 22 5.5 132 0.0 1020 1025 1022 6.7 5.5 Sunny intervals all day
11 10.5 18.4 14.5 51 89 70 5.4 10.1 7.8 18 3.2 76 0.0 1022 1025 1023 2.8 3.2 Sunny intervals all day
12 6.9 17.6 12.3 52 88 70 2.7 8.7 5.7 21 4.9 119 0.0 1021 1023 1022 4.3 6.8 Sunny intervals all day
13 3.1 16.1 9.6 58 91 75 0.2 8.9 4.6 18 2.6 62 0.0 1018 1023 1021 2.7 5.8 Sunny intervals all day
14 3.2 15.8 9.5 54 91 73 0.4 8.2 4.3 23 5.3 126 0.0 1019 1024 1021 2.1 7.8 Sunny intervals all day
15 5.1 16.4 10.8 51 89 70 1.5 7.8 4.7 22 5.8 140 0.7 1024 1028 1026 2.7 7.4 Sunny intervals all day
16 11.1 17.2 14.2 64 86 75 6.7 10.3 8.5 27 8.1 195 0.0 1023 1027 1025 9.1 3.7 Sunny intervals all day
17 10.3 15.6 13.0 72 86 79 6.3 11.1 8.7 19 4.8 116 0.0 1019 1024 1021 8.9 0.0 Cloudy all day
18 12.1 17.4 14.8 61 89 75 6.2 12.7 9.5 22 4.5 107 0.0 1014 1019 1017 12.2 1.1 Cloudy am, sunny ints pm
19 3.5 18.9 11.2 45 91 68 0.7 7.7 4.2 14 2.4 57 0.0 1016 1020 1018 2.2 9.0 Sunny intervals all day
20 5.8 18.8 12.3 54 88 71 2.2 10.1 6.2 19 3.0 77 0.0 1018 1020 1019 3.8 6.4 Sunny intervals all day
21 3.4 17.9 10.7 63 91 77 0.5 10.8 5.7 22 5.3 127 0.0 1014 1021 1018 2.3 4.0 Sunny intervals all day
22 8.7 16.8 12.8 49 87 68 5.0 10.5 7.8 31 8.8 210 2.6 1012 1022 1017 5.9 9.0 Sunny intervals all day
23 7.9 17.1 12.5 65 88 77 3.9 11.0 7.5 34 6.7 160 0.0 1017 1023 1020 5.6 2.1 Sunny ints am, cloudy pm,
24 6.0 18.1 12.1 42 84 63 2.5 6.6 4.6 18 5.8 128 0.0 1021 1028 1024 3.8 11.5 Sunny intervals all day
25 3.2 18.4 10.8 52 90 71 -0.6 9.8 4.6 23 5.3 125 0.0 1013 1029 1021 1.7 11.1 Sunny intervals all day
26 10.1 14.8 12.5 71 89 80 6.1 9.6 7.9 34 8.6 207 1.8 1007 1015 1011 6.0 1.4 Showers am, sunny ints pm
27 7.5 16.3 11.9 48 84 66 4.0 5.9 5.0 22 7.1 172 0.0 1015 1021 1018 5.1 12.8 Sunny intervals all day
28 7.4 15.8 11.6 65 84 75 3.1 10.8 7.0 21 5.1 121 0.0 1013 1020 1017 5.8 0.2 Brief sunny intervals all day
29 12.3 20.4 16.4 62 85 74 9.0 12.6 10.8 21 5.8 138 0.0 1012 1014 1013 9.6 4.8 Cloudy am, sunny ints pm
30 13.3 15.4 14.4 60 91 76 4.8 11.8 8.3 20 5.6 135 1.5 1009 1013 1011 4.3 2.5 Drizzle am, sunny ints pm
31 3.7 17.5 10.6 49 90 70 0.9 7.2 4.1 21 5.7 139 0.9 1013 1027 1020 2.4 12.6 Sunny intervals all day
8.0 17.4 12.7 57 88 72 3.9 10.0 7.0 23 5.9 4364 39.8 1015 1020 1017 5.6 172.6  

Graphs for May 2011

Figure 1. Temperature and Rainfall for May 2011.
Figure 2. Sunshine, air pressure and mean wind speed for May 2011.
Figure 3. Wind direction for May 2011.
Figure 4. Soil & sea surface temperature (SST) for Lyme Bay for May 2011.
Figure 5. Wind run, maximum gusts and mean pressure for May 2011.