Autumn 2009

The River Tavy high up on Dartmoor on a bright and breezy November day.
The River Tavy high up on Dartmoor on a breezy November day.
Summary for Autumn 2009
Mean Max: 15.9 oC  
Mean Min: 8.7 oC  
Mean: 12.3 oC  
High Max: 22.7 oC 12th Sep
Low Max: 7.0 oC 30th Nov
High Min: 16.6 oC 8th Sep
Low Min: 1.2 oC 18th Oct
Mean Grass Min: 5.9 oC  
Grass Min: -2.2 oC 16th Oct
Rain Total (gauge): 302.7 mm  
Rain Total (tipping bucket): 281.7 mm  
Rain Days >0.2: 45 Days  
Rain Days >1.0: 38 Days  
Max 24 hrs: 16.6 mm 20th Oct
Days without any rain: 46 Days  
Air Frost: 0 Days  
Ground Frost: 5 Days  
Snow Falling: 0 Days  
Snow (50%) @ 9am: 0 Days  
Thunder Heard: 5 Days  
Hail <5 mm: 0 Days  
Hail >5 mm: 0 Days  
Fog @ 9am: 2 Days  
Total Monthly Sunshine: 383:07:00 h:m:s  
Total Monthly Sunshine: 383.1


Most Sunshine in a Day: 12:26 Hours  
Average Daily Sunshine: 04:12 Hours  
Sunless Days: 7 Days  
Cloudless Days: 13 Days  
Total Possible Sunshine: 1039:03:00 h:m:s  
Percentage of Total Sun: 37 %  
Mean Soil Temp @ 30 cm: 12.1 oC  
Min Soil Temp @ 30 cm: 7.7 oC 29th Nov
Max Soil Temp @ 30 cm: 15.1 oC 1st Sep
Mean Soil Temp @ 100 cm: 13.0 oC  
Min Soil Temp @ 100 cm: 10.7 oC 30th Nov
Max Soil Temp @ 100 cm: 15.2 oC 1st Sep
Wind >39 mph:


N: 12.64 Days  
NE: 5.69 Days  
E: 5.43 Days  
SE: 13.99 Days  
S: 13.04 Days  
SW: 15.17 Days  
W: 10.19 Days  
NW: 6.18 Days  
Calm: 34.38 Days  
Mean Wind: 4.0 mph  
Max Gust: 47 mph 13th Nov
Mean Cloud Cover: 55 %  
Mean RH @ 9am: 84 %  
Rain Duration >0.1mm/hour: 148.5 Hours  
Frost Duration: 0.0 Hours  
Max Frost Duration in a Day: 0.0 Hours  
Mean Sea Temperature: 15.1 oC  
Normal for Month:   oC  
Max Sea Temperature: 17.3 oC 1st Sep
Min Sea Temperature: 11.9 oC 30th Nov
Mean Pressure @ 9am: 1017.8 hPa  
Mean Pressure: 1013.2 hPa  
Max Pressure: 1037.1 hPa 11th Sep
Min Pressure: 975.6 hPa 29th Nov
Max Dewpoint: 16.8 oC 7th Sep
Min Dewpoint: -2.5 oC 30th Nov
Mean Dewpoint: 8.4 oC  
Max Humidity: 93 % 6th Oct
Min Humidity: 48 % 11th Sep
Mean Humidity: 80 %  


An warm autumn of contrasts with September being dry & sunny; October was average and November very wet and windy. Overall this autumn was much warmer than 2007 & 2008, but slightly cooler than 2006.

The autumn started more like summer with September being dominated by warm, sunny and dry weather. This lead into a non-descript October but things livened up considerably in November.

Total rainfall was 303 mm which is less than last year but more than 2007.
A rather un-thundery September & October but November changed things with 4 thundery days.
Sunshine total was 383 hours which is more than 2008 but rather less than 2007.
Soil temperatures were generally around normal.
Wind directions were dominant from the south-west.
Rain duration was 148.5 hours, most of which was from November.
As expected, sea temperatures gradually fell through the Autumn.
Overall mean pressure was around average.
Dewpoints were generally quite high at times due to the dominance of warm, south-westerly air streams.
The warm, dry air during September meant that average relative humidity ended up being slightly below normal.

Graphs for Autumn 2009

Figure 1. Temperature and Rainfall for Autumn 2009.
Figure 2. Sunshine, air pressure and mean wind speed for Autumn 2009.
Figure 3. Wind direction for Autumn 2009.
Figure 4. Soil & sea surface temperature (SST) for Lyme Bay for Autumn 2009.