Monthly Climate Summary for September 2009 at Chesham (Tennis Club)
                          home daily
                            Unsettled start, then dry and rather warm with sunny periods       back forward
                         
Overall mean temperature was 13.4 ēC which is   degC compared with the 1971-2000 average  
Mean day maximum (09-21) was 18.6 ēC which is   degC compared with the 1971-2000 average  
Mean night minimum (21-09) was 8.1 ēC which is   degC compared with the 1971-2000 average  
Mean 24hr maximum (09-09) was 18.6 ēC                
Mean 24hr minimum (09-09) was 8.1 ēC                
  Highest day max was 25.7 ēC on  the   8            
  Lowest day max was 15.4 ēC on  the 17            
  Highest night min was 16.3 ēC on  the 8            
  Lowest night min was 1.4 ēC on  the 27            
  Lowest grass min was   ēC on  the              
                         
Total rainfall this month was 15.6 mm which is   per  cent of the 1971-2000 average    
  Highest daily fall was 12.4 mm on  the 2            
Number of hours with rain was                    
Equiv. TSR rainfall duration was 4.7 hrs which is   per  cent of the 1971-2000 average    
  Highest no of wet hrs   hrs on  the              
  Highest duration 3.8 hrs on  the 2            
  Mean rainfall intensity 3.35 mm/hr                
                         
Total est sunshine this month was 131.9 hrs which is   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 7.8 hrs on  the 12            
                         
Maximum  snow depth  was   cm on  the               
                         
Mean sea-level pressure at 09Z 1022.3 mbar which is   mbar compared with the 1961-1990 average  
  Highest pressure at 09Z 1037.5 mbar on  the 11            
  Lowest  pressure at 09Z 998.2 mbar on  the 3            
                         
Total number of days with:                      
Air Frost 0   0.2mm rain 7   No  sun 1   Snow lying      
Grnd Frost 0   1.0mm 2   3h  sun 23   Snow/sleet 0    
Max < 0ēC 0   5mm 1   6h  sun 8   Hail 0    
Max > 10 30   10mm 1   9h  sun 0   Thunder 0    
Max > 20 5   25mm 0   12h sun 0   Fog at 09Z 0    
Max > 30 0         15h sun 0   Gale 0    
                         
Notable events during the month: