Monthly Climate Summary for September 2011  at Hampstead
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     A rather changeable month with near-normal temperatures, but a very warm end   back forward
                       
Overall mean temperature was 16.1 ēC which is +1.8 degC compared with the 1971-2000 average
Mean day maximum (09-21) was 20.3 ēC              
Mean night minimum (21-09) was 12.0 ēC              
Mean 24hr maximum (09-09) was 20.3 ēC which is +2.0 degC compared with the 1971-2000 average
Mean 24hr minimum (09-09) was 12.0 ēC which is +1.6 degC compared with the 1971-2000 average
  Highest day max was 27.9 ēC on  the   30          
  Lowest day max was 15.4 ēC on  the 18          
  Highest night min was 16.5 ēC on  the 10          
  Lowest night min was 6.7 ēC on  the 18          
  Lowest grass min was 4.1 ēC on  the 15          
                       
Total rainfall this month was 43.9 mm which is 66.5 per  cent of the 1971-2000 average  
  Highest daily fall was 14.0 mm on  the 6          
Number of hours with rain was 42.0 hrs              
Equiv. TSR rainfall duration was 29.4 hrs which is 79.5 per  cent of the 1971-2000 average  
  Highest no of wet hrs 6.0 hrs on  the 5          
  Highest equiv duration 5.0 hrs on  the 5          
Mean Rainfall Intensity 1.49 mm/h              
                       
Total sunshine this month was 139.2 hrs which is 106.7 per  cent of the 1971-2000 average  
Equiv. C/S sunshine total was 153.1 hrs which is 106.7 per  cent of the 1971-2000 average  
  Highest daily sun was 9.7 hrs on  the 29          
                       
Maximum  snow depth  was 0.0 cm              
                       
Mean sea-level pressure at 09Z 1015.0 mbar which is -1.7 mbar compared with the 1961-1990 average
  Highest pressure at 09Z 1030.3 mbar on  the 27          
  Lowest  pressure at 09Z 1001.8 mbar on  the 12          
                       
Number of days with:                    
Air Frost 0   0.2mm rain 14   No  sun 2   Snow lying 0  
Grnd Frost 0   1.0mm 9   3h  sun 22   Snow/sleet 0  
Max < 0ēC 0   5mm 3   6h  sun 10   Hail 0  
Max > 10 30   10mm 1   9h  sun 3   Thunder 0  
Max > 20 15   25mm 0   12h sun 0   Fog at 09Z 0  
Max > 30 0         15h sun 0   Gale 0  
                       
Notable events during the month: