Monthly Climate Summary for December 2009 at Hampstead

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Mild and changeable till the 10th; very cold and wintry 16th-25th

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Overall mean temperature was

3.5

ºC

which is

-1.5

degC

compared with the 1971-2000 average

Mean day maximum (09-21) was

5.6

ºC

Mean night minimum (21-09) was

1.7

ºC

Mean 24hr maximum (09-09) was

6.0

ºC

which is

-1.5

degC

compared with the 1971-2000 average

Mean 24hr minimum (09-09) was

1.0

ºC

which is

-1.5

degC

compared with the 1971-2000 average

Highest day max was

11.2

ºC

on  the

9

Lowest day max was

0.3

ºC

on  the

18

Highest night min was

9.5

ºC

on  the

6

Lowest night min was

-4.4

ºC

on  the

19

Lowest grass min was

-9.8

ºC

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 < 0ºC

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: