September 2017
A Dartmoor stream near Hound Tor on a humid and cool late September day

A cool and wet month with well below average sunshine
Summary for  September 2017
Mean Max: 18.9ºC (-0.2ºC)
Mean Min: 10.5ºC (-0.4ºC)
Mean (min+max ÷ 2): 14.7ºC (-0.3ºC)
Mean (integrated):  13.9ºC  
High Max: 23.1ºC 4th
Low Max: 16.9ºC 16th
High Min: 16.6ºC 4th
Low Min: 3.4ºC 22nd
Mean Grass Min: N/A  
Grass Min: 1.2ºC 22nd
Days  >20°C 6 Days  
Days >15°C 30 Days  
Nights  >10°C 16 Days  
Nights  <5°C 3 Days  
Rain Total (gauge): 87.1 mm (153%)
Rain Total (tipping bucket): 85.8 mm (151%)
Rain Days >0.2 mm: 21 Days  
Rain Days >1.0 mm: 15 Days  
Max 24 hrs: 21.1 mm 3rd
Days without any rain: 9  
Air Frost: 0 Days  
Grass Frost: 0 Days  
Snow Falling: 0 Days  
Snow (50%) @ 9am: 0 Days  
Ice Days: 0 Days  
Thunder Heard: 1 Day 16th
Hail <5 mm: 1 Day 16th
Hail >5 mm: 0 Days  
Fog @ 9am: 1 Day 18th
Total Monthly Sunshine: 137.0 Hours (77%)
Most Sunshine in a Day: 12.2 Hours 1st
Average Daily Sunshine: 4.6 Hours  
Sunless Days: 3 Days  
Cloudless Days: 1 Day 1st
Total Possible Sunshine: 378.1 Hours  
Percentage of Total Sun: 36%  
Maximum UV Index: 5.1 4th
Time of Max UV:    
Average Max UV: 3.4  
Mean Soil Temp @ 30 cm: 16.8ºC  
Min Soil Temp @ 30 cm: 13.9ºC 2nd
Max Soil Temp @ 30 cm: 17.8ºC 23rd
Mean Soil Temp @ 100 cm: 16.2ºC  
Min Soil Temp @ 100 cm: 15.1ºC 1st
Max Soil Temp @ 100 cm: 16.8ºC 27th
Ave 10 Min Wind >39 mph: 0.00 Days  
N: 3.79 Days 12%
NE: 0.57 Days 2%
E: 0.38 Days 1%
SE: 2.19 Days 7%
S: 6.96 Days 22%
SW: 2.28 Days 7%
W: 2.04 Days 7%
NW: 4.65 Days 15%
Calm: 7.12 Days 26%
Wind Chill Low: 3.2ºC 22nd 
Mean Wind: 3.8 mph  
Max Gust: 37 mph 12th
Mean Cloud Cover: 57%  
Mean RH @ 9am: 92%  
Rain >0.1mm/hour: 18.5 Hours  
Frost Duration: 0.0 Hours  
Air Frost in a Day: 0.0 Hours 1st
Mean Sea Temperature: 17.0ºC (-0.1ºC)
Normal for Month: 17.1ºC  
Max Sea Temperature: 18.2ºC 2nd
Min Sea Temperature: 16.2ºC 23rd
Mean Pressure @ 9am: 1014.3 hPa  
Mean Pressure: 1014.0 hPa  
Max Pressure: 1025.2 hPa 2nd
Min Pressure: 993.8 hPa 11th
Max Change in 24 hours: 13.6 hPa 3rd
Radiation Daily Mean: 10.34 MJ/m²  
Max Daily Value: 19.32 MJ/m² 1st
Min Daily Value: 3.27 MJ/m² 3rd
Number of Days with Data: 30 Days  
1-Hour Maximum: 824 1st
Starting Time of the Hour:   12:00
Max Dewpoint: 19.7ºC 4th
Min Dewpoint: 3.0ºC 22nd 
Mean Dewpoint: 12.2ºC  
Max Humidity: 100%  
Min Humidity: 50% 1st
Mean Humidity: 86%  
Weather Data for Otter Valley, Devon. September 2017
  Temp oC Grass Hum (%) Soil oC DP (oC) Wind (mph) Rain Air (hPa) W/m² UV Sun Frost Calm Wind Sea Observations
  Min Max Min Min Max 30 100 Min Max Max Ave Run mm Min Max Max Max Hours Hours Hours Chill Temp
1 11.1 22.6 N/A 50 99 N/A N/A 10.5 14.6 13 2.0 49 0.0 1020 1025 876 4.5 12.2 0.0 6.7 10.8 17.9 Sunny intervals all day
2 7.3 20.6 N/A 60 100 N/A N/A 6.8 14.4 16 2.6 62 0.0 1019 1025 928 5.0 7.1 0.0 7.1 6.6 17.8 Rain all day
3 12.1 17.1 N/A 82 100 N/A N/A 10.2 17.1 26 7.5 180 21.1 1006 1019 144 1.6 0.0 0.0 0.1 9.4 17.8 Brief sunny intervals all day
4 16.6 23.1 N/A 78 100 N/A N/A 16.3 19.7 15 3.1 73 0.7 1007 1015 754 5.1 1.3 0.0 10.8 16.4 17.9 Sunny intervals all day
5 16.2 20.2 N/A 82 99 N/A N/A 12.7 19.2 24 5.9 142 1.5 1011 1018 520 3.4 2.3 0.0 0.0 14.2 18.0 Sunny intervals all day
6 9.9 20.3 N/A 59 100 N/A N/A 9.5 14.0 17 2.0 49 0.0 1019 1022 799 5.1 7.9 0.0 12.5 9.7 17.9 Brief sunny intervals all day
7 11.4 19.3 N/A 74 99 N/A N/A 10.4 15.9 18 2.1 51 0.0 1011 1022 490 3.2 0.3 0.0 11.8 11.2 17.8 Brief sunny intervals all day
8 14.6 19.1 N/A 78 98 N/A N/A 10.9 16.5 14 3.4 81 7.3 998 1011 622 4.2 0.9 0.0 2.9 11.7 17.7 Sunny intervals all day
9 9.3 18.5 N/A 74 100 N/A N/A 8.7 14.7 18 2.0 48 7.3 999 1004 1016 4.4 5.8 0.0 10.1 9.0 17.6 Brief sunny intervals all day
10 8.6 17.1 N/A 82 100 N/A N/A 8.2 16.1 26 4.1 99 1.1 996 1005 416 3.1 1.0 0.0 10.0 8.2 17.4 Sunny intervals all day
11 11.6 17.8 N/A 73 96 N/A N/A 9.4 14.8 34 5.7 137 3.7 994 1003 880 4.3 5.8 0.0 0.0 10.3 17.2 Sunny intervals all day
12 9.0 18.3 N/A 66 99 N/A N/A 8.2 14.6 37 5.7 137 1.3 999 1010 815 4.2 4.8 0.0 5.5 8.4 17.1 Sunny intervals all day
13 11.3 18.6 N/A 57 99 N/A N/A 8.2 15.8 29 5.5 132 0.7 998 1005 833 4.1 7.3 0.0 1.6 11.1 16.9 Sunny intervals all day
14 6.2 18.1 N/A 66 100 N/A N/A 5.5 13.6 24 3.0 73 3.3 1004 1017 881 4.2 6.7 0.0 5.3 5.9 16.6 Sunny intervals all day
15 6.7 19.4 N/A 63 100 N/A N/A 6.2 13.2 13 1.5 35 4.6 1014 1018 945 4.0 7.4 0.0 13.3 6.4 16.5 Sunny ints, thunderstorm pm
16 4.7 16.9 N/A 75 100 N/A N/A 4.3 13.8 10 1.1 27 0.9 1012 1015 969 3.8 5.1 0.0 10.4 3.7 16.4 Sunny intervals all day
17 7.6 19.2 N/A 60 100 N/A N/A 7.1 12.4 13 1.9 46 0.0 1012 1018 871 3.8 9.6 0.0 8.1 6.9 16.3 Sunny intervals all day
18 4.8 18.7 N/A 64 100 N/A N/A 4.4 13.5 14 1.9 45 0.0 1018 1021 650 3.1 6.8 0.0 5.6 4.5 16.4 Sunny intervals all day
19 7.3 19.7 N/A 59 100 N/A N/A 6.7 13.9 16 1.3 32 0.0 1021 1023 862 4.0 6.4 0.0 14.8 7.1 16.4 Sunny ints am, cloudy pm
20 10.8 17.2 N/A 81 100 N/A N/A 9.9 15.0 22 5.1 121 4.0 1016 1022 461 3.1 1.9 0.0 10.3 10.5 16.4 Rain am, sunny intervals pm
21 14.1 18.2 N/A 70 100 N/A N/A 7.7 15.1 23 7.4 177 5.3 1012 1019 813 3.4 4.3 0.0 2.0 8.7 16.3 Sunny ints, cloudy evening
22 3.4 18.2 1.2 76 100 N/A N/A 3.0 14.4 22 4.7 114 0.9 1019 1021 806 3.7 5.1 0.0 9.4 3.2 16.3 Sunny intervals all day
23 14.4 19.6 N/A 74 99 N/A N/A 12.7 15.8 20 6.9 166 0.4 1018 1021 730 3.5 7.5 0.0 0.0 11.8 16.4 Cloudy all day
24 15.3 18.3 N/A 88 98 N/A N/A 13.8 16.8 19 3.6 87 0.0 1015 1018 414 2.4 0.0 0.0 3.3 15.0 16.5 Sunny intervals all day
25 13.6 21.8 N/A 71 99 N/A N/A 12.4 17.2 14 1.8 44 0.7 1017 1022 773 0.0 3.1 0.0 6.8 13.0 16.5 Sunny intervals all day
26 11.4 17.8 N/A 82 100 N/A N/A 10.9 15.5 9 1.2 29 0.0 1021 1023 393 2.3 3.3 0.0 10.7 11.2 16.6 Cloudy am, rain pm
27 14.1 17.2 N/A 89 100 N/A N/A 12.4 15.9 24 5.8 140 5.1 1014 1021 265 2.1 0.0 0.0 2.5 12.7 16.6 Sunny intervals all day
28 9.6 18.7 N/A 80 100 N/A N/A 9.2 16.3 20 4.4 106 4.6 1014 1019 719 0.0 8.7 0.0 6.8 9.4 16.7 Sunny intervals all day
29 13.6 17.1 N/A 70 100 N/A N/A 8.5 16.8 22 4.0 99 6.2 1013 1018 519 2.2 3.4 0.0 4.9 9.4 16.6 Brief sunny intervals all day
30 8.6 18.2 N/A 78 100 N/A N/A 7.8 14.9 28 5.6 129 5.3 1011 1018 598 3.0 0.8 0.0 6.8 8.4 16.5 Rain am, sunny intervals pm
10.5 18.9 1.2 72 100 16.8 16.2 9.1 15.4 20 3.8 2710 85.8 1011 1017 692 3.4 137.0 0.0 200 9.5 17.0  
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