The Weather at Durham in 2009

Despite a very cold December, 2009 was one of the warmest years on record at Durham, 14th equal warmest in 160 years. And despite eight months of below-average rainfall, the annual total was still well above average, with exceptionally high rainfall in July and November. July 17th (64.2mm) was the sixth wettest day on record at Durham since 1850.

The year started with the coolest January since 2001 but temperatures were above average nevertheless, despite feeling much worse! There was the lowest absolute maximum (10.8°C) since 2001 and the lowest absolute minimum (-5.8°C) since 2004. There was the largest number of ground frosts since 1998. The 12-month average was now down to 9.08°C, the lowest since the 12-month period ending Sept 2001. It was drier than normal, although both 2005 and 2006 were drier than January 2009. February was a relatively mild month after a cool January. It was the 117th warmest in 160 years, so not quite in the upper quartile. Curiously, there was a ground frost every night to the 15th, but only one thereafter. It was a little drier than normal. It was the first February since 2000 with sun every day, but overall sunshine hours were below average. The average Winter temperature was 3.9°C, 0.5°C above average. It was the 96th warmest winter since 1850 – 51, not exceptional therefore. It was the 65th driest winter since 1850 – 51 with a total rainfall of 132mm, 26mm below average. The 6-month rainfall was now back to average but the 12-month total remained well above average.

March was the 15th warmest 1850, although 2000, 2002, 2003 were all warmer. The warmest March on record is 1938 (9.2°C). There was the 12th highest maximum (17.2°C) for a March day since 1900 (18th), the warmest March day since 1991. However, there were the most ground frosts for March since 1980 and the lowest absolute grass minimum since 1950 (when available records begin for that variable), implying cold, clear nights. The mean minimum temperature was above average, but not greatly so. It was the driest March since 2003, the 35th driest March on record since 1850. The driest March was in 1953 (1.3mm). There were the fewest number of rain days since 2004. The last three months have been the driest three months since Aug – Oct 2007, while the last six months have been the driest six-month period since April – September 2006. Looking at a slightly longer period, November to March inclusive, it has been the 36th driest period since 1850/51; 1999/2000 and 2003/4 were drier. For the second month in a row, all days recorded sunshine. It was the 4th sunniest March since 1882, beaten only by 2003, 1907 and 1894.

April was the 8th warmest at Durham since 1850. Even so, mean air temperatures were higher in 2003, 2004 and 2007! It was the 8th highest mean maximum – exceeded in 2003 and 2007 – and the 15th highest mean minimum temperature. It would have been a very dry month except for the fall of 23.2mm on the 28th of which 18.2mm fell steadily over 8 hours during the evening. Temperatures in May were well above average too, although the mean air temperature was 0.1°C below that last year. The mean maximum temperature was the highest since 2004. The absolute minimum temperature (2.9°C) was the highest since 1986. It was the first May with no ground frosts since 2003. For the 7th month in a row, rainfall was below average. The 3- and 6-month totals were now both well below average, but with the totals from last June and July still in the sum, the 12-month total remained well above average. It was the sunniest May since 2001. With only February having been very slightly below average, cumulative sunshine hours were now well ahead of average. It was a breezy month with above-average wind speed, equal to 2003 and the windiest May since 2000. There was a gust of 77 kph on the 7th. Not surprisingly, it was the 5th equal warmest Spring (with 2002) on record at Durham. Other than 1945, the other warmest springs have all been in this decade: 2003, 2004 and 2007.

June had the 29th highest mean maximum temperature since 1900 but with the mean minimum being exactly average, mean air temperature was, overall, only a little above average. There was the lowest grass minimum since 1999, but no ground frost within Durham City all month. There were some warm spells: at the beginning of the month, in the middle (Durham Regatta weekend), 22nd – 24th and at the end of the month. In between were some cooler days. The maximum on the 5th of only 8.3°C deserves some mention; we do not compile a list of lowest maximum temperature in each month but if we did, this would surely be close to the record! Rainfall was well above average, ending a run of 7 months of below-average rainfall. It was wetter than last June, but much less wet than June 2007. Overall, June 2009 ranks 135th wettest in 160 years (since 1850). June was less sunny than in May. It was sunnier last June but there was less sun in June 2007. June was a calm month with average wind speed well below average. The maximum gust was only 59.6km/h on the 19th.

The most extraordinary weather episode in July occurred on the 17th when very high rainfall caused severe flooding in Durham; the University’s Maiden Castle sports centre was inundated for only the 3rd time since being built in the early 1960s. The rain began on the 16th with a fall of 11.6mm in one hour (1400 – 1500 GMT): altogether 15mm fell that day. A total of 64.2mm was recorded on the 17th; there were only 3 hours that were completely dry. Remarkably, 6.6mm fell between 1400 and 1500 GMT and 9.2mm in the next hour. The highest gust of the month was recorded during this period. 17th July 2009 is the 6th wettest day on record at Durham since 1850. The last time this total was exceeded was 25th August 1986 when 69.2mm fell. The wettest day on record at Durham is 11th September 1976 with 87.8mm. All this rain meant the 4th wettest July on record, easily beating last year (134mm), but still exceeded by 1930 (183.9mm), 1867 (184.9mm) and 1888 (206.6mm). It was the 17th wettest month on record since 1850. Interestingly, 8 of these 17 have been in summer, 4 in autumn and five in winter, none in spring; this reflects the fact that Durham tends to have wet summers (marginally wetter than autumn) with a tendency to heavy falls of rain. As a result, all long-term rainfall totals are now well above average again. In terms of temperature, July (26.8°C) was an unexceptional month, a little above average in all respects; only 13 days had a maximum above 20°C. The absolute maximum on the 1st was the highest since 2006, but thereafter temperatures were not exceptional. The absolute minimum was the highest since 2004.

It was the warmest August since 2003, and the equal 22nd warmest since 1850. Minimum temperatures were a little higher above average than maximum temperatures. August was a dry month, equal 53rd driest since 1850. Nevertheless, it was the 11th wettest Summer on record since 1850. When we note that 2008 was the 8th wettest and 2007 was the 14th wettest, the last three summers have been disappointingly wet therefore! These are the three wettest summers in a row at Durham since records began in 1850. 2004 was the 10th wettest summer too. This decade has therefore seen a complete reversal of the very dry summers of the 1990s. The mean air temperature for the summer as a whole was the same as last year, 14.9°C, equal 30th warmest since 1850.

September temperatures were well above average, especially during the day. It was the 23rd equal warmest in 160 years and included the highest September temperature since 2004 (23.7°C on the 12th). It was the 12th driest September since 1850 with the fewest number of rain days (with 2003) since records began in 1950. Nevertheless, it was a little sunnier than normal. October was mild, particularly so at the end of the month with maximum temperatures above 15°C on the last four days. It was the 23rd equal warmest October in 160 years. Rainfall was again below average and the 3-month total was now well below average again, although the 6-month total remained above average. Despite the mildness and below-average rainfall, it was less sunny than usual. It was also a less windy month than normal, but there was a gust of 91.6kph on the 3rd. It was the 11th equal warmest November on record since 1850. 2001 and 2003 were equally warm, 2006 was warmer! Daytime temperatures reached double figures on no less than 17 days and there were no ground frosts, even on the seemingly “very cold” nights at the end of the month. It was also the 2nd wettest November since 1850, only exceeded by November 1965 when a total of 185.9mm was recorded. Indeed, this was the 24th highest month total for all months since January 1850 (n = 1919), so only about 1% of months are this wet in Durham. Nevertheless, compared to July, no one day contributed the majority; there were falls over 25mm on 1st (26mm) and 29th (27.2mm). In all, there were 22 rain days (>0.25mm) and 18 wet days (>1mm). Not surprisingly, all long-term totals were now above average again, most notably the 6-month total. And despite all the rain, sunshine was just a little above average. Overall, it was the 8th warmest autumn at Durham, but 2001, 2005 and 2006 were all warmer. It was only the 48th wettest autumn at Durham, despite November, but in this decade only 2000 has been (much) wetter.

After a mild November, December was the complete reverse – very cold indeed. December was not nearly as wet as November (still well above average) but most of the precipitation in the second half of the month fell as snow. We no longer keep records of “snow lying” but this must have been the month with the highest number of days with snow lying for well over a decade. December 2009 was the only month below average temperature in the whole year. It was the coldest December since 1995 (1.8°C) – indeed the coldest of any month since then, a run of 168 months in all. Mean maximum temperature was the lowest for December since 1996 and mean minimum temperature the lowest since 1995. It was the =30th coldest December in 160 years; all things being equal, this would mean a December like this every five years on average but of course with global warming a December this cold is now much more unusual, more like once every 15 years perhaps. Nevertheless, there were several days above 10°C at the start of the month, the last as late as the 10th. The absolute minimum air temperature (-7.8°C) was the lowest only since 2001. Despite all the precipitation, December was sunnier than normal.

Notwithstanding a cold December, the year as a whole saw an average mean air temperature of 9.5°C, the 14th equal warmest in 160 years. In this decade only 2000, 2001 and 2008 have been colder. All years this decade are in the top 21 warmest out of 160 years. One very cold month right at the end of 2009 could not disguise the fact that this has been the warmest decade on record at Durham since 1850. Given the exceptionally wet July and November, this meant that 2009 as a whole was also well above average in terms of rainfall total, even though eight months were below average. It was the 32nd wettest year at Durham since 1850 (749.1mm). This decade only 2000 (873.2mm) and 2008 (817.1mm) have been wetter. There were 176 rain days – the most since 2000. 2009 was the sunniest year since 2003, just above average.

January February March April May June July August September October November December Year
Mean air temperature 3.4 4.7 6.8 8.9 11.3 13.5 15.4 15.8 13.6 10.5 7.5 2.4 9.5
Difference from average 0.4 1.5 1.8 1.9 1.4 0.5 0.5 1.1 0.9 0.7 1.8 -1.5 0.9
Mean maximum 5.9 7.5 11 13.7 16 18.3 19.7 20.1 18 14 10.5 5.2 13.3
Mean minimum 0.8 1.9 2.6 4.1 6.6 8.6 11.1 11.5 9.2 6.9 4.4 -0.5 5.6
Absolute maximum 10.8 13.8 17.2 18.6 23 25.6 26.8 24.4 23.7 16.4 14.5 10.6 26.8
Absolute minimum -5.7 -4 -5.3 -0.7 2.9 3.5 8 8.9 4.8 0 0.2 -7.8 -7.8
Number of ground frosts 24 16 23 20 0 0 0 0 0 4 12 22 121
Rainfall 39.4 35.6 21.2 36.8 38.2 80.6 167.4 39.2 14.4 39.0 153.8 83.6 749.2
Highest daily rainfall 6.6 17.8 10.6 23.2 9.4 10.4 64.2 12 5.6 9.6 27.2 12.2 64.2
Number of rain days 16 9 8 8 15 19 22 14 4 14 22 25 176
Sunshine hours 80.1 65.1 176.2 151.8 192.5 131.7 131 129.2 106.4 75.1 73.8 70.2 1383.1
Max daily sunshine 7 7.5 11.4 12.6 11.8 11.7 11.7 9.5 10.2 7.9 5.8 6.5 11.8
Mean windspeed (kph) 12.6 11.3 15.0 12.6 14.8 7.8 12.4 14.1 10.9 10.9 10.7 No Data 12.1

Professor Tim Burt
Department of Geography
Durham University