Cool September, but sunnier and drier than average

Armagh Observatory reports that September 2015 was cooler than average. The mean temperature was slightly less than 12.8 degrees Celsius (approximately 55.0 F). The result contrasts with each of the last two Septembers, and indeed most Septembers during the last 20 years. This September's mean temperature was 0.5 degrees C cooler than the most recent 30-year (1981-2010) average September at Armagh, namely 13.25 C. There were four ground frosts, which occurred on the 13th, 22nd, 27th and 28th, the coldest of which (-1.2 C) occurred on the 28th. There were no air frosts. The warmest day was 21.4 C, which occurred on the 29th, and the coldest night (lowest minimum air temperature) was 3.4 degrees Celsius on the 16th.

September 2015 was also slightly sunnier than average, with a total of 125.0 hours of strong sunshine recorded at Armagh. Although this was only 9.6 per cent more than the most recent 30-year (1981-2010) average number of hours of strong sunshine at Armagh (114.0 hours), the month was the sunniest September for 18 years, that is, since September 1997. The sunniest day was the 28th, with 9.7 hours of strong sunshine.

The month was also much drier than average, with a total recorded precipitation, including four trace values, of 30.5 mm (1.2 inches). This is less than half (just 44.8 per cent) of the most recent 30-year (1981-2010) average September precipitation at Armagh. The wettest day was the 11th, which had a total precipitation of 15.0 mm (nearly 0.6 inches) and contributed nearly half the month's total rainfall.

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; URL: http://climate.arm.ac.uk

Last Revised: 2015 October 5th