Monthly Climate Summary for December 2009 at Hampstead  
                        home daily
                     Mild and changeable till the 10th; very cold and wintry 16th-25th   back forward
                       
Overall mean temperature was 3.5 ēC which is -1.5 degC compared with the 1971-2000 average
Mean day maximum (09-21) was 5.6 ēC              
Mean night minimum (21-09) was 1.7 ēC              
Mean 24hr maximum (09-09) was 6.0 ēC which is -1.5 degC compared with the 1971-2000 average
Mean 24hr minimum (09-09) was 1.0 ēC which is -1.5 degC compared with the 1971-2000 average
  Highest day max was 11.2 ēC on  the   9          
  Lowest day max was 0.3 ēC on  the 18          
  Highest night min was 9.5 ēC on  the 6          
  Lowest night min was -4.4 ēC on  the 19          
  Lowest grass min was -9.8 ēC on  the 20          
                       
Total rainfall this month was 89.1 mm which is 135.0 per  cent of the 1971-2000 average  
  Highest daily fall was 13.1 mm on  the 29          
Number of hours with rain was 138.0 hrs              
Equiv. TSR rainfall duration was 96.6 hrs which is 169.5 per  cent of the 1971-2000 average  
  Highest no of wet hrs 16.0 hrs on  the 30          
  Highest equiv duration 13.3 hrs on  the 30          
                       
Total sunshine this month was 75.9 hrs which is 168.7 per  cent of the 1971-2000 average  
Equiv. C/S sunshine total was 83.5 hrs which is 168.7 per  cent of the 1971-2000 average  
  Highest daily sun was 6.3 hrs on  the 10          
                       
Maximum  snow depth  was 10.0 cm on the 22          
                       
Mean sea-level pressure at 09Z 1006.3 mbar which is -8.7 mbar compared with the 1961-1990 average
  Highest pressure at 09Z 1033.0 mbar on  the 12          
  Lowest  pressure at 09Z 984.7 mbar on  the 22          
                       
Number of days with:                    
Air Frost 11   0.2mm rain 27   No  sun 4   Snow lying 7  
Grnd Frost 16   1.0mm 17   3h  sun 12   Snow/sleet 7  
Max < 0ēC 0   5mm 6   6h  sun 3   Hail 0  
Max > 10 6   10mm 3   9h  sun 0   Thunder 0  
Max > 20 0   25mm 0   12h sun 0   Fog at 09Z 4  
Max > 30 0         15h sun 0   Gale 0  
                       
Notable events during the month: