May 2004

Temperatures
(all temperatures in degrees Celsius; all averages 1961 – 1990)

Mean daily maximum: 16.3
Difference from average: +2.0

Mean daily minimum: 6.3
Difference from average: +0.8

Mean air temperature: 11.3
Difference from average: +1.3

Mean grass minimum: 7.0

Absolute grass minimum: -0.4 (26th)

Number of ground frosts: 1

Number of air frosts: 0

Mean soil temperature at 30cm depth: 13.4

Mean soil temperature at 100cm depth: 11.6

Rainfall
(all totals in millimetres; all averages 1961 – 1990)

Total for the month: 19.8
Difference from average: -32

Percentage of the average: 38%

Wettest day: 9.4 (25th)

Number of rain days (>0.25mm): 6

Number of wet days (=> 1mm): 3

3-month total rainfall to 31st May: 134.8
Difference from average: -16.4

6-month rainfall total to 31st May: 306.2
Difference from average: -2.9

12-month rainfall total to 31st May: 541.9
Difference from average: -107.1

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 70.6%

Sunshine
(all averages 1961 – 1990)

Total for the month: 163.7 hours
Difference from average: -4.8

Percentage of the average: 97.1%

Mean daily sunshine: 5.3 hours
Difference from average: -0.1

Sunniest day: 13.1 hours (23rd)

Number of days with no recorded sunshine: 3

Cumulative total sunshine since 1st January: 474.8 hours
Difference from average: -51.5

Wind

The mean wind speed: 10.2km/h [5.5kt]
Difference from average: -2.2km/hr

The highest gust: 55.6km/h [45kt] from 255° at 14:16 GMT on 3rd

ISSN1350-483

Comments on May 2004
Equipment problems have proven a problem in recent weeks. On comparison with other stations, I have decided that the rainfall data for March and April are questionable; until I can make corrections based on the nearby Barker’s Haugh gauge, I am using Dave O’Hara’s figures for Ferryhill. I have assumed that the gauge was working OK all month, although there is some doubt about totals recorded in the first few days of the month. The Met Office declared the temperature figures for 1-24 May to be too high; I have assumed the same deviation from average as at Copley (Ken Cook). In both cases, faulty equipment has been replaced.

Assuming equivalent conditions to Copley, mean maximum was the 9th equal highest for May since 1950 whilst overall mean air temperature was the 17th highest or May since 1850.

May was a dry month, although not particularly sunny. Long-term rainfall totals remain below average, as does the cumulative sunshine total for 2004.

Professor Tim Burt
Department of Geography
Durham University