Monthly Climate Summary for  May  2009  at Hampstead  
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                               A changeable month with a warm sunny finish   back forward
                       
Overall mean temperature was 13.2 ēC which is +1.3 degC compared with the 1971-2000 average
Mean day maximum (09-21) was 17.6 ēC              
Mean night minimum (21-09) was 8.8 ēC              
Mean 24hr maximum (09-09) was 17.8 ēC which is +1.5 degC compared with the 1971-2000 average
Mean 24hr minimum (09-09) was 8.7 ēC which is +1.1 degC compared with the 1971-2000 average
  Highest day max was 24.1 ēC on  the   31          
  Lowest day max was 12.0 ēC on  the 4          
  Highest night min was 14.2 ēC on  the 29          
  Lowest night min was 3.9 ēC on  the 4          
  Lowest grass min was -1.1 ēC on  the 4          
                       
Total rainfall this month was 30.6 mm which is 51.8 per  cent of the 1971-2000 average  
  Highest daily fall was 14.1 mm on  the 25          
Number of hours with rain was 36.0 hrs              
Equiv. TSR rainfall duration was 25.2 hrs which is 70.0 per  cent of the 1971-2000 average  
  Highest no of wet hrs 10.0 hrs on  the 25          
  Highest equiv duration 8.3 hrs on  the 25          
Mean rainfall intensity 1.21 mm/h              
                       
Total sunshine this month was 181.7 hrs which is 100.9 per  cent of the 1971-2000 average  
Equiv. C/S sunshine total was 199.8 hrs which is 100.9 per  cent of the 1971-2000 average  
  Highest daily sun was 12.1 hrs on  the 30          
                       
Maximum  snow depth  was 0.0 cm on the            
                       
Mean sea-level pressure at 09Z 1019.3 mbar which is +4.1 mbar compared with the 1961-1990 average
  Highest pressure at 09Z 1033.5 mbar on  the 29          
  Lowest  pressure at 09Z 1002.9 mbar on  the 15          
                       
Number of days with:                    
Air Frost 0   0.2mm rain 13   No  sun 2   Snow lying 0  
Grnd Frost 2   1.0mm 7   3h  sun 25   Snow/sleet 0  
Max < 0ēC 0   5mm 1   6h  sun 14   Hail 0  
Max > 10 31   10mm 1   9h  sun 7   Thunder 0  
Max > 20 7   25mm 0   12h sun 2   Fog at 09Z 0  
Max > 30 0         15h sun 0   Gale 0  
                       
Notable events during the month: