Coldest May for nearly 20 Years

Armagh Observatory, 3 June 2015. Armagh Observatory reports that with a mean temperature of 9.85 degrees Celsius, May 2015 was much cooler than average. This was the coldest May since 1996.

There were several very cold nights, notably the minimum air temperature recorded on the 1st, which was -1.5 C. This was the coldest May night since 1996 and the tenth coldest May night on record, that is, since 1843 when maximum-minimum thermometers first began to be used at Armagh. There were also several very sharp ground frosts, notably the minimum grass temperature of -7.1 C recorded on the 1st, and that of -6.9 C recorded on both the 4th and 16th, and 15 ground frosts in total. The warmest day (highest maximum air temperature) was 17.6 C on the 22nd.

The month was also much wetter than average, with a total precipitation of 93.85 mm including 3 trace values. This was more than 60% wetter than the most recent (1981-2010) average May rainfall at Armagh, and the wettest May since 2006. The wettest day was the 2nd, with 24.8 mm rainfall. Rain fell on at least 26 days of the month.

May 2015 was slightly duller than average, with 167 hours of strong sunshine, approximately 12% fewer than the long-term (1881-2010) May average at Armagh but only 4% fewer than the most recent (1981-2010) 30-year May average. The sunniest day was the 13th, with a total of 13.4 hours of strong sunshine.

May marks the end of the meteorological Spring (March, April and May). Each of these months was cooler than average, leading to a mean Spring temperature of 8.0 degrees Celsius, approximately the same as the long-term (1796-2010) average Spring temperature at Armagh, but nearly 0.8 C cooler than the most recent (1981-2010) 30-year Spring average.

Both March and April were sunnier than average, but May slightly duller, leading to a total of 509 hours of strong sunshine for the three months, which is approximately 12% more than the long-term (1881-2010) Spring average and 23% more than the most recent (1981-2010) 30-year Spring average at Armagh. 2015 was the ninth sunniest Spring on record and the sunniest Spring since 2008.

Precipitation this Spring was approximately 23% more than the long-term (1838-2010) Spring precipitation at Armagh, and 13.5% more than the most recent (1981-2010 Spring average.

These data refer to observations at Armagh Observatory, which has been recording the weather at Armagh since 1795.

FOR FURTHER INFORMATION PLEASE CONTACT: Mark Bailey at the Armagh Observatory, College Hill, Armagh, BT61 9DG. Tel.: 028-3752-2928; FAX: 028-3752-7174; mebat signarm.ac.uk.

Last Revised: 2015 June 4th