September 2005

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

Mean daily maximum: 18.2
Difference from average: +1.5

Mean daily minimum: 10.0
Difference from average: +1.3

Mean air temperature: 14.1
Difference from average: +1.4

Absolute maximum: 22.2 (12th)

Absolute minimum: 2.9 (24th)

Mean grass minimum: 7.5

Absolute grass minimum: -0.3 (23rd)

Number of ground frosts: 1

Number of air frosts: 0

Mean soil temperature at 30cm depth:

Mean soil temperature at 100cm depth:

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

Total for the month: 63.8
Difference from average: +8.2

Percentage of the average: 115%

Wettest day: 15.2 (8th)

Number of rain days (>0.25mm): 10

Number of wet days (=> 1mm): 9

3-month total rainfall to 30th September: 173.7
Difference from average: -28.4

6-month rainfall total to 30th September: 297.9
Difference from average: -28.4

12-month rainfall total to 30th September: 553.1
Difference from average: -104

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 75%

Sunshine
(all averages 1961 – 1990)

Total for the month: 145 hours
Difference from average: +21.1

Percentage of the average: 117%

Mean daily sunshine: 4.8 hours
Difference from average: +0.7

Sunniest day: 9.8 hours (12th)

Number of days with no recorded sunshine: 3

Cumulative total sunshine since 1st January: 1104.3 hours
Difference from average: -20.1

Wind

The mean wind speed: 13.7km/h [7.4kt]
Difference from average: +1.4km/hr

The highest gust: 77km/h [41.6kt] from 199° at 17:05 GMT on 13th

ISSN1350-483

Comments on September 2005
The automatic weather station failed to operate after a power cut on 14th August. This fault was not discovered until 7th September. Mean temperatures (in italics) have been estimated using anomaly maps on the Met Office website. The first six days of the month were dry at Barker’s Haugh; the rainfall figures reported here are for the Durham Observatory therefore.

If an anomaly of 1.4°C above average is accepted, then a mean air temperature of 14.1°C for September makes it one of the warmest on record at Durham since 1850. It ranks 8th highest on record, the highest since 1999 (which ranks 3rd). Unusually, apart form 1999, none of the other very warm Septembers have been recent: three years from the 1890s and two from the 1940s rank above September 2005, plus 1865. The warmest September at Durham was in 1949 (15.3°C).

September was a little wetter than average. The wettest day was the 8th with 15.2mm but in total 30mm fell on the 7th and 8th combined. Despite the rainfall, sunshine was a little above average too, and the cumulative average has nearly reached the average figure for the first time this year.

Professor Tim Burt
Department of Geography
Durham University