May 2015 summary

May’s weather was dominated by Atlantic lows, with high pressure never really getting established, and the consequence was a cool, wet and windy month with the temperature reaching 20C just once – we usually see something higher than that on about five days during the month.

It wasn’t our wettest May – this year we recorded 80mm of rainfall, well above average for May, but last year was wetter with 96.4mm. Nor was it our coolest: the average temperature was 11.6C which is about 1C below normal, but May 2013 was cooler still with 10.8C. It was, however, the windiest May we have recorded since the station was set up, with a wind run of 2807nm and a gust of 33kts on the 18th, also a new record for May.

As well as rainfall from fronts associated with the procession of Atlantic lows, there were heavy convective showers on the 3rd, the 14th (the wettest day of the month, when funnel clouds were seen a few miles to the south) and the 19th. A very distinct cold front, associated with a low to the north of Scotland, passed through on the morning of the 29th and in the space of five minutes the temperature dropped 3C, the pressure rose 1.7hPa, the wind gusted to 24kts and 5.8mm of rain fell. Anyone caught out in that got drenched. This was followed by convective showers, thunder in the Wells area and a soaking for the Bath and West Show.

The end of May also marks the end of meteorological Spring. The average temperature for Spring 2015 was normal at 9.6C, and the rainfall total of 145.4mm was close to average too – the wet May was offset by a dry April. Even if this wasn’t quite the wettest or coolest May we have seen it still qualifies as disappointing, but Spring 2015 was unexceptional.