Monthly Climate Summary for  May 2009 at Chesham (Tennis Club)
                          home daily
                         A rather changeable month, but with a warm sunny finish       back forward
                         
Overall mean temperature was 11.7 ēC which is +0.1 degC compared with the 1971-2000 average  
Mean day maximum (09-21) was 17.3 ēC which is +0.9 degC compared with the 1971-2000 average  
Mean night minimum (21-09) was 6.1 ēC which is -0.6 degC compared with the 1971-2000 average  
Mean 24hr maximum (09-09) was 17.3 ēC                
Mean 24hr minimum (09-09) was 6.0 ēC                
  Highest day max was 24.4 ēC on  the   31            
  Lowest day max was 12.4 ēC on  the 4            
  Highest night min was 11.7 ēC on  the 28            
  Lowest night min was -0.6 ēC on  the 10            
  Lowest grass min was   ēC on  the              
                         
Total rainfall this month was 32.7 mm which is 61.5 per  cent of the 1971-2000 average    
  Highest daily fall was 13.7 mm on  the 14            
Number of hours with rain was                    
Equiv. TSR rainfall duration was 8.8 hrs which is 29.6 per  cent of the 1971-2000 average    
  Highest no of wet hrs   hrs on  the              
  Highest duration 1.9 hrs on  the 17            
  Mean rainfall intensity 3.74 mm/hr                
                         
Total est sunshine this month was 157.9 hrs which is 85.5 per  cent of the 1971-2000 average    
Equiv. C/S sunshine total was   hrs which is   per  cent of the 1971-2000 average    
  Highest daily sun was 8.8 hrs on  the 30            
                         
Maximum  snow depth  was 0.0 cm on  the               
                         
Mean sea-level pressure at 09Z 1018.1 mbar which is +3.0 mbar compared with the 1961-1990 average  
  Highest pressure at 09Z 1032.0 mbar on  the 29            
  Lowest  pressure at 09Z 1000.9 mbar on  the 15            
                         
Total number of days with:                      
Air Frost 2   0.2mm rain 11   No  sun 2   Snow lying 0    
Grnd Frost 0   1.0mm 8   3h  sun 24   Snow/sleet 0    
Max < 0ēC 0   5mm 2   6h  sun 12   Hail 0    
Max > 10 31   10mm 1   9h  sun 0   Thunder 0    
Max > 20 7   25mm 0   12h sun 0   Fog at 09Z 0    
Max > 30 0         15h sun 0   Gale 0    
                         
Notable events during the month: