Over the current standard 30 year average period, 1981-2010, the mean temperature at the Radcliffe Observatory Oxford site was 10.7°C (mean daily maximum 14.6°C, mean daily minimum 6.9°C). January and February tie as the coldest months of the year on average (mean temperature 4.9°C), while July is the warmest (mean temperature 17.9°C). Since continuous records of both daily maximum and minimum temperature commenced in April 1815, the coldest night was 24 December 1860, when the minimum temperature fell to 17.8°C. Within the last 50 years, the coldest night was 14 January 1982, when the temperature reached -16.6°C. The hottest day on the record was 19 August 1932, when the maximum temperature of 35.1°C was recorded: this was equalled on 3 August 1990.
The annual average precipitation is 660 mm, falling on an average of 165 days per year. The driest period of the year is late winter to early spring (February average 43 mm) and the wettest period is autumn (October average 70 mm), but with wide variations from year to year. The wettest day on record (since 1827) was 10 July 1968, when 87.9 mm fell in the 24 hours commencing 0900 GMT. Since 1968, the wettest day has been 67.3 mm on 27 June 1973. In the monthly rainfall record for Oxford extending back to 1767, the wettest month (September 1774) received 224 mm and the wettest year (2012) 979 mm. No calendar month has ever remained completely dry, the driest months since 1767 being April 1817 and April 2011, both of which received just 0.5 mm. The driest years were 1788 (337 mm, just 51 per cent of the current average) and 1921 (381 mm). Snow can be expected to fall on around 16 days in a typical year, with the ground snow-covered on six or seven mornings. The greatest known snow depth was 61 cm which fell in February 1888. Thunderstorms occur on around 10 days per annum, most frequently during the summer half-year.
The average annual sunshine duration is 1577 hours, about 35 per cent of the possible duration of daylight at this latitude. Contrary perhaps to perceived wisdom, sunshine is recorded on almost twice as many days per year (300, on average) as measurable rainfall (165). Since sunshine records commenced in February 1880, the dullest month on record has been December 1890, with just 5.0 hours of bright sunshine during the month (an average of less than 10 minutes per day); contrast this with July 1911, the sunniest month on record, when 310 hours of sunshine was recorded, an average of 10 hours daily.
Burt, Stephen and Burt, Tim, 2019. Oxford Weather and Climate since 1767. Oxford University Press, 544pp.