# Annual Summary 2023

**The weather at Durham in 2023**

**A very warm and very wet year!**

Despite some cold days in the middle of the month, this was the 23^{rd} mildest **January** since 1844, with the 22^{nd} highest mean maximum and the equal 25^{th} highest mean minimum air temperature. There were no ‘ice days’ when the maximum remained below 0°C. There were 12 ground frosts, the 16^{th} lowest number since 1875. It was drier than normal, the 61^{st} driest January since 1850. It was not as sunny as January 2022, the sunniest January on record at Durham, but nevertheless the total was well above average, making this the second sunniest January on record since 1874!

Altogether, **February** was a remarkably mild month, the 2^{nd} warmest on record since 1844, surpassed only in 1998 (7.6 °C). Both the mean maximum and the mean minimum are 3^{rd} highest on record. The mean maximum has only been exceeded in 1998 and 2019; the mean minimum only in 1846 and 1998. The maximum temperature (15.7 °C) on the 20^{th} is the sixth warmest February day on record; the minimum temperature (9.0 °C) on the 2^{nd} is the 28^{th} warmest February night. 2023 is one of nine Februarys to have had only four air frosts since 1850; six Februarys have had just three air frosts with three having just two, including last year. There was the equal 2^{nd} lowest total number of ground frosts since 1874. It was a relatively dry month, the 34^{th} lowest total for February since 1850. There was no measurable precipitation at all in the first half of the month. The wettest day of the month (31^{st}) saw a total of only 5.4 mm. Sunshine was just a little above the 1991-2020 average but nevertheless the 31^{st} highest February total since 1881.

For the **winter** as a whole, despite a below-average December, this was the 15^{th} mildest winter (mean air temperature: 5.0 °C) on record at Durham since 1844, although not as warm as the previous winter (5.4 °C) which ranks equal 4^{th} warmest. There were 27 air frosts, 9 more than last year, but only 36 ground frosts, 16 below average, the sixth lowest total since 1874, and 7 fewer than last year. It was a relatively dry winter (116.4 mm), 73% of normal, ranking 58^{th} driest out of a total of 173 winters. The winter was sunnier than normal (250 hours, 122%) compared to the 1991-2020 average. Nevertheless, it still ranks 5^{th} overall since 1880, just slightly less sunny than the previous winter (254 hours) which ranks 4^{th}. These two sunny winters show just how much the clarity of the atmosphere has improved compared to most of the record, given significant reductions in the concentration of particulate matter in the air.

It is not that unusual for **March** to be colder than February: this has happened 38 times in 180 years; this year March was 0.4 °C colder than February. It was decidedly a month of two halves; the daily maximum temperature did not exceed 10 °C until the 12^{th}, with a maximum of only 2.7 °C on the 9^{th}. Much milder conditions in the second half of the month meant that, overall, the mean air temperature for the whole month was just above average. Despite seeming disappointing, March 2023 had the same mean air temperature as March 2020, both being warmer than two other recent Marches: March 2018 (4.1 °C) and March 2013 (2.4 °C). It was in fact the equal 141^{st} warmest March in 180 years. The mean daily maximum was exactly average (1991-2020), whilst the mean daily minimum was a little above average. Whilst generally not bitterly cold, the minimum temperature on the night of the 8^{th} (-7.0 C) is nevertheless the equal 48^{th} coldest March night on record since 1850 (n=5394). It is unusual that the number of air frosts equalled the number of ground frosts. Rainfall was above average, the equal 118^{th} wettest March since 1850. There was measurable rainfall on 28 days, the highest total ever recorded for March at Durham since 1850, but there was no day without measurable sunshine. Even so, the amount of sunshine was below average. Only 5 Marches have been duller this century, the most recent in 2018.

**April **was very much an ‘average’ month with mean air temperature, precipitation total and total hours of bright sunshine all very close to the 1991-2020 average. This was only the second month since September 2021 to experience below-average temperature. Nevertheless, it ranks as the 40^{th} warmest April in 180 years of record. The absolute temperature range (16.9 °C) was remarkably small, equal 18^{th} lowest since 1844, equal to that in April 2001 and the lowest since April 1986 (15.9 °C). The absolute maximum is the lowest for April since 2001 (14.8 °C) and the 22^{nd} lowest since 1844. This was the 117^{th} wettest April since 1850, 12.7 mm above the median value. Only 24 Aprils have had fewer air frosts since 1844. For the 0900 observations, there were 7 days with winds from the north-east and altogether 12 days with winds in the quadrant from north to east. Like April, there was a preponderance of winds from the north-east in **May**. At 0900 GMT, four days experienced winds exactly from the north-east, and in total 14 days saw winds at 0900 from the north-east quadrant (i.e. between north and east). May was a warm month, the sixth equal warmest May on record, with the seventh warmest mean maximum and the tenth warmest mean minimum. The absolute minimum of 2.7 °C is the 10^{th} highest on record. May was a relatively dry month, the 37^{th} driest in 174 years, so well into the lowest quartile. No measurable rainfall was recorded in the last 13 days of the month. The number of hours of bright sunshine was almost exactly average; nevertheless, the cumulative amount of sunshine so far this year remains well above average.

With March and April both close to average temperature, and only June well above, even so this was the 13^{th} warmest **spring** on record since 1844 (8.9 °C, 0.4 °C above average). Both mean maximum (21^{st} highest) and mean minimum (equal 8^{th} highest) were also 0.4 °C above average. Even so, there were no very high temperatures this spring with a maximum of only 21.2 °C; 104 springs have had higher absolute maxima since 1844! It was the 87^{th} driest spring in 174 years (130.6 mm) but rainfall was frequent with 56 rain days, the 10^{th} equal highest total. It was the 53^{rd} sunniest spring since 1882 (440.3 hours), 21 hours (95%) below average.

The mean air temperature for **June** 2023 (15.5 °C) is the 4^{th} highest on record since 1844, exceeded only in 1940 (15.7 °C), 1858 (15.8 °C) and 1846 (17.5 °C). In the extended Eglise series, which goes back to 1784, June 2023 ranks 7^{th}; the additional warmer Junes are 1818, 1822 and 1826. It is still not clear why hot Junes have been largely absent in the last 150 years and yet were much more common before that. Whilst 1846 is very early in the Durham record, we can be confident about its mean air temperature: June 1846 remains the hottest June in the Central England Temperature record with a mean air temperature of 18.2 °C. Since June 2022 and June 2021 were also very warm, perhaps we are reverting to June weather last seen in the second quarter of the 19^{th} Century? The mean maximum temperature for June 2023 is the 3^{rd} highest on record at Durham, surpassed only in 1940 (22.3 °C) and 1846 (22.6 °C). The mean minimum temperature is the equal 5^{th} highest since 1844. The absolute maximum of 27.3 °C on the 12^{th} is the 28^{th} warmest June day since 1844 and the warmest since 2017 (n=5336). After some cooler days at the start of the month, every day except 2 saw a maximum of at least 20 °C; the total of 19 days is the same as in 1970 and only exceeded in 1846 (21) and 1940 (23). For the number of days with a maximum of at least 25 °C, 2023 is one of 10 Junes to see 4 days over this threshold; 1976 had 7, 1940 had 8 and 1846 had 10. Apart from two days recording 0.2 mm (6^{th} and 17^{th} June), the dry spell lasted from 19^{th} May to 18^{th} June. It ended in spectacular style with a daily total of 19.6 mm on the 18^{th}, which included two consecutive hourly totals of 10 mm and 5.2 mm. Although my record of hourly rainfall for Durham from 1997 is not complete (about 7% of data is missing), the hourly total of 10 mm ranks 22^{nd} in a list of over 200,000 hours. Had it not been for those two days with 0.2 mm totals, the 30-day dry spell would have been exceptional, the 3^{rd} longest on record. All three long-period rainfall totals are now below average. This was the 7^{th} sunniest June on record, based on a prediction using Met Office E&NE regional data. The poor exposure of the solarimeter in the summer months is shown by the fact that the estimated amount of bright sunshine was just 155.1 hours whereas as the estimated total is 232 hours.

**July **was the first month of the year with below-average mean air temperature. Nights were warmer than average, but days were disappointingly cool, with only 2 days above 25 °C (which is the average number for the month, but nevertheless a disappointing total). The weather was doubly disappointing given how hot the previous two Julys have been. It was the 13^{th} wettest July since 1850, with 24 rain days. As expected, sunshine was below average, but not excessively so, the 50^{th} dullest July since 1882. Like July, **August** was a disappointing month for temperatures. There was just one day with a maximum above 25 °C compared to an average of 2; in August 2022 we had 6 days above 25 °C! The mean air temperature was just above the 1991-2020 average, and it was the equal 33^{rd} warmest August since 1844, so not too bad looking at the long record, but 11 Augusts have been warmer since 2000. There was one rain day fewer than normal, but even so it was a wet month, with 125% of average, the 39^{th} wettest August since 1868. Although disappointingly wet, it was nowhere near the wettest August on record at Durham: 175.7 mm in 1956, but still in marked contrast to just 13 mm last year! The fall of 33.4 mm on the 14^{th} is the 21^{st} wettest August day since 1850 (n = 5394). The sunshine total was just below average and there were 4 days with no recorded sunshine. Again, the contrast with August 2022 is notable: a total of 221.6 hours of bright sunshine.

It was the 12^{th} warmest **summer** on record (15.62 °C; average 15.0 °C), thanks in large part to the very warm June. The warmest day of the summer was nevertheless in July (27.8 °C, 8^{th} July). July was marginally the warmest month, but all three months had very similar mean air temperatures (15.51 °C, 15.74 °C July, 15.68 °C August). Only 7 days exceeded 25 °C, 4 of them in June, rather disappointing compared to 14 last year but still 2 better than average. Despite a dry June, it was a wet summer (246.6 mm, 130% of average, 21^{st} wettest since 1868). July especially and August were duller than average, but a very sunny June meant that overall, the total amount of summer sunshine was just a little above average (107%). The Davis summer index generates a value of 729, only the 44^{th} best summer since 1900 therefore, and confirming the generally disappointing summer weather despite an exceptional June. The Davis Summer Index for 2022 (809) ranks third behind 1995 (813) and 1976 (831); no wonder we noticed the difference this year!

**September **started with some very hot days and even with the expected cooler days later in the month, this still ends up the 2^{nd} equal warmest September (with 2021) on record since 1843, surpassed only in 2006 (15.9 °C). The mean maximum is the third highest on record for September, higher than July’s or August’s this year but lower than June’s. There were four days with a maximum of at least 25 °C, the equal 2^{nd} highest September total (with 1898), one less than the record in 1959. However, there was technically no ‘heatwave’ as there were not three days in a row that reached 25 °C. There have been four September heatwaves at Durham since records began: in 1868, 1880, 1906 and 1959. The mean minimum temperature was the 4^{th} highest for September since 1843 (11.2 °C), exceeded only in 2006 (11.8° C), 2021 (11.4 °C) and 2016 (11.3 °C). The minimum temperature of 16.5 C on the 11^{th} is the 4^{th} warmest September night on record; three Septembers share the highest minimum of 17.2 °C: 1945, 1949 and 2016. As might be expected, there was also the 4^{th} highest mean grass minimum for September since 1874 (9.7 °C), exceeded only in 2021 (11.4 °C), 2000 (10.4 °C) and 2016 (9.8 °C). A fall of 7.4 mm on 10^{th} September brought to an end a dry spell of 13 days. The wettest day was the 14^{th} with 11.4 mm. Both the number of rain days and the month’s total were close to average. Sunshine was above average, the total of 145.6 hours being just into the upper quartile (n=141).

Like September, **October **started unusually mild but, of course, it cooled off steadily through the month with a maximum below 10 °C by the 20^{th} (9.4 °C). Even so, overall, it was an above-average month for temperature, night-time temperatures more so than daytime temperatures. The mean air temperature (10.69 °C) is the 24^{th} highest on record for October since 1844 (n=181), but it was more than a degree cooler than 2022 (11.78 °C), and overall nine Octobers have been warmer this century. Soil temperatures remain relatively high; there were only 4 ground frosts and one air frost. It was a very wet month, more than twice the average amount (230%), the fourth wettest October on record since 1868 (fifth wettest since 1850 if we include 160.2 mm in October 1865, during a period of some uncertainty about the Durham rainfall observations). Only 1903 (201.8), 1960 (172.5 mm) and 1896 (148.8 mm) have had wetter Octobers in Durham since 1868. The total of 22 rain days is the equal 21^{st} highest on record, not exceptionally high, implying that rain per rain day was very high this month; indeed, the rain per rain day of 6.7 mm/day is the 7^{th} equal highest for October on record since 1868. Storm Babet produced a total of 35.2 mm on the 20^{th}, the 10^{th} highest daily total on record for October. Also associated with Storm Babet, there was a very strong gust of wind of 85.3 kph just after noon on the 20^{th}. Not surprisingly, October was a dull month, well below average for hours of bright sunshine, the 32^{nd} lowest total since 1880 (n=143).

Mean air temperature in **November** was only 0.2 °C above average; nevertheless, this was the 42^{nd} warmest November on record since 1843, so just into the upper quartile. Like the previous two autumnal months, November started very mild, but the end of the month was distinctly chilly. Even so, the absolute maximum came quite late in the month, 14.7 °C on the 23^{rd} being the equal 85^{th} warmest November day on record in over 3600 November days. There were 9 grass frosts, the equal 32^{nd} lowest total on record. Precipitation was again above average, the equal 39^{th} wettest November on record. However, sunshine was also above average, the 27^{th} sunniest November since 1880.

It was a very mild **autumn**, the mean air temperature of 10.98 °C being the 7^{th} highest on record. It was also a very wet autumn, the 13^{th} wettest on record since 1868 (286.2 mm), just a few millimetres less than last year, 92 mm above average, almost half as much again as the average amount. Notwithstanding the high rainfall, the amount of sunshine was only just below average (297.2 hours, 99% of average).

Notwithstanding some cold days at the start of the month, including an ‘ice day’ on the 2^{nd} (maximum temperature -0.7 °C), this was the 15^{th} warmest **December** on record since 1843. The mean maximum is the equal 15^{th} highest and the mean minimum the equal 13^{th} highest. Christmas Eve was the equal 32^{nd} warmest December day since 1843 (n=5611). This was the 11^{th} wettest December since 1850. Remarkably, the total of 38 mm recorded on the 4^{th} is the wettest December day on record, beating the previous record: 37.4 on 16^{th} December 1872 (1872 is the second wettest year at Durham, behind 2012). The estimated amount of sunshine was 43.7 hours although in fact the AWS recorded 61.7 hours, showing that exposure during the winter months is OK. There was a gust of 98.2 kph on the 21^{st}.

Following last year’s record-breaking mean air temperature (10.59 °C), **2023** was the 2^{nd} warmest year on record (10.35 °C). Not surprisingly, the decadal running mean has now reached 9.9 °C, easily the highest on record. Of the individual months, only April fell below mean air temperature. This was the sixth wettest year on record (837.2 mm, 157mm above average, 123%), the wettest year since the record-holder 2012 (1018 mm). Summer and particularly autumn were well above average, winter and spring below average. Sunshine hours were just a little above average (103%, 1508 hours).