Monthly Climate Summary for  January 2010 at Chesham (Tennis Club)
                          home daily
                Very cold and snowy first half; less cold and changeable second half       back forward
                         
Overall mean temperature was 0.8 ēC which is   degC compared with the 1971-2000 average  
Mean day maximum (09-21) was 3.0 ēC which is   degC compared with the 1971-2000 average  
Mean night minimum (21-09) was -1.4 ēC which is   degC compared with the 1971-2000 average  
Mean 24hr maximum (09-09) was 3.0 ēC                
Mean 24hr minimum (09-09) was -1.9 ēC                
  Highest day max was 7.9 ēC on  the   17            
  Lowest day max was -1.5 ēC on  the 7            
  Highest night min was 4.1 ēC on  the 23            
  Lowest night min was -8.6 ēC on  the 4            
  Lowest grass min was   ēC on  the              
                         
Total rainfall this month was 62.0 mm which is   per  cent of the 1971-2000 average    
  Highest daily fall was 11.0 mm on  the 28            
Number of hours with rain was                    
Estimated rainfall duration* was 22.2 hrs which is   per  cent of the 1971-2000 average    
  Highest no of wet hrs   hrs on  the              
  Highest duration 4.0 hrs on  the 28            
  Mean rainfall intensity 2.80 mm/hr                
                         
Total est sunshine this month was 21.5 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 4.1 hrs on  the 30            
                         
Maximum  snow depth  was 0.0 cm on  the               
                         
Mean sea-level pressure at 09Z 1014.9 mbar which is +0.3 mbar compared with the 1961-1990 average  
  Highest pressure at 09Z 1040.2 mbar on  the 26            
  Lowest  pressure at 09Z 990.0 mbar on  the 29            
                         
Total number of days with:                      
Air Frost 21   0.2mm rain 16   No  sun 14   Snow lying 0    
Grnd Frost 0   1.0mm 13   3h  sun 2   Snow/sleet 0    
Max < 0ēC 7   5mm 4   6h  sun 0   Hail 0    
Max > 10 0   10mm 1   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:                  
                         
*Rainfall duration is the aggregate of 5-min sampling intervals with 0.2mm or more            
Davis AWS rainfall multiplied by 1.1 to achieve closest match with manually read rainfall