Monthly Climate Summary for December 2009 at Chesham (Tennis Club)
                          home daily
                          Mild and unsettled till the 10th; very cold and wintry 16th-25th       back forward
                         
Overall mean temperature was 2.3 ēC which is   degC compared with the 1971-2000 average  
Mean day maximum (09-21) was 5.1 ēC which is   degC compared with the 1971-2000 average  
Mean night minimum (21-09) was -0.6 ēC which is   degC compared with the 1971-2000 average  
Mean 24hr maximum (09-09) was 5.1 ēC                
Mean 24hr minimum (09-09) was -2.0 ēC                
  Highest day max was 10.5 ēC on  the   9            
  Lowest day max was -1.3 ēC on  the 19            
  Highest night min was 8.0 ēC on  the 6            
  Lowest night min was -13.4 ēC on  the 21            
  Lowest grass min was   ēC on  the              
                         
Total rainfall this month was 92.2 mm which is   per  cent of the 1971-2000 average    
  Highest daily fall was 18.2 mm on  the 29            
Number of hours with rain was                    
Equiv. TSR rainfall duration was 31.9 hrs which is   per  cent of the 1971-2000 average    
  Highest no of wet hrs   hrs on  the              
  Highest duration 6.4 hrs on  the 29            
  Mean rainfall intensity 2.89 mm/hr                
                         
Total est sunshine this month was 5.9 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 1.0 hrs on  the 13            
                         
Maximum  snow depth  was   cm on  the               
                         
Mean sea-level pressure at 09Z 1005.9 mbar which is   mbar compared with the 1961-1990 average  
  Highest pressure at 09Z 1033.2 mbar on  the 11            
  Lowest  pressure at 09Z 985.4 mbar on  the 22            
                         
Total number of days with:                      
Air Frost 15   0.2mm rain 18   No  sun 18   Snow lying 0    
Grnd Frost 0   1.0mm 14   3h  sun 0   Snow/sleet 0    
Max < 0ēC 4   5mm 8   6h  sun 0   Hail 0    
Max > 10 2   10mm 2   9h  sun 0   Thunder 0    
Max > 20 0   25mm 0   12h sun 0   Fog at 09Z 0    
Max > 30 0         15h sun 0   Gale 0    
                         
Notable events during the month: