August 2004

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

Mean daily maximum: 20.1
Difference from average: +1.0

Mean daily minimum: 12.5
Difference from average: +2.2

Mean air temperature: 16.3
Difference from average: +1.6

Absolute maximum: 25.4 (7th)

Absolute minimum: 5.9 (22nd)

Mean grass minimum: 10.5

Absolute grass minimum: 1.7 (22nd)

Number of ground frosts: 0

Number of air frosts: 0

Mean soil temperature at 30cm depth: 18.2

Mean soil temperature at 100cm depth: 16.8

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

Total for the month: 156.8
Difference from average: +89.7

Percentage of the average: 234%

Wettest day: 52.2 (9th)

Number of rain days (>0.25mm): 19

Number of wet days (=> 1mm): 16

3-month total rainfall to 30th August: 289.6
Difference from average: +104.9

6-month rainfall total to 30th August: 405.3
Difference from average: +83.3

12-month rainfall total to 30th August: 806.7
Difference from average: +157.7

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 79.9%

Sunshine
(all averages 1961 – 1990)

Total for the month: 123.4 hours
Difference from average: -32.1

Percentage of the average: 79.3%

Mean daily sunshine: 4 hours
Difference from average: -1.0

Sunniest day: 10.7 hours (8th)

Number of days with no recorded sunshine: 2

Cumulative total sunshine since 1st January: 859.5 hours
Difference from average: -141

Wind

The mean wind speed: 9.3km/h [5kt]
Difference from average: -2.4km/hr

The highest gust: 55.6km/h [30kt] from 266° at 13:13 GMT on 27th

ISSN1350-483

Comments on August 2004
August was a warm but very wet month. Mean air temperature was 1.6°C above average, lower than last year, but still 11th highest since 1850. Mean minimum temperature was 2nd highest on record since 1950. The minimum on the night of the 8th / 9th was 16.8°C, a remarkably high value, and the next night was only marginally cooler. For the summer as a whole, an average temperature of 15.2°C places 2004 as the 14th warmest on record since 1850, following last year’s record breaker.

Most remarkable was the rainfall, more than twice the monthly average. The total of 156.8mm is the 6th highest for August since 1852, exceeded only in 1917, 1927, 1878, 1986 and 1956 (the August record with 175.7mm). The total of 52.2mm on the 9th was only the 14th daily total at Durham since 1881 of 50mm or over. 72.2mm fell on the 9th and 10th, associated with a decaying hurricane, and altogether 88.4mm fell in four days (9th – 12th). There was also a daily catch of 25mm on the 19th. For the summer as whole, it was the 11th wettest on record (289.6), and the wettest since 1997. 1867 holds the summer rainfall record with 383.4mm; summers tended to be relatively wetter in the late 19th Century. Not surprisingly, long-term totals are now well above average, and the 12 – month running total is the highest since October 2001.

Sunshine was again below average, another disappointing month, and the cumulative total for the year is now well below average.

Professor Tim Burt
Department of Geography
Durham University