Our May started off unsettled, with plenty of showers. Indeed, during the second week, with low pressure in charge, we had three days when the country was hit by frequent heavy thunderstorms. Only one of these hit Epping full square, on the 9th, when heavy rain, hail, thunder and lightning gave us 22.4mm of rain, the 6th wettest May day of our 39 years of records.

But then pressure built and by the middle of the month we had a ‘blocking high’ firmly set to the north-west of Britain, bringing us almost continual north-east or east winds for the remainder of the month. These were dry winds, but cool, and often brought cloudy weather which some days burnt off to give a sunny afternoon, but often didn’t. With no rain after 19th, we ended up with a dry month at 34.8mm, well below the long term average of 56.1mm.

Consequently, the maximum temperature for the month was a comparatively cool 21.6°C – only five other Mays in our records had a lower monthly maximum temperature.

But although the month felt frequently cloudy and cool, it wasn’t a cold May: overall, the mean temperature was almost bang on average at 12.5°C, and the lowest recorded for the month was 4.3°C, almost two degrees above the long term average, so no frosts or even ground frosts this May.

With high pressure stuck for the second half of the month over the North Atlantic, and winds circulating clockwise around it, no surprise that north-easterly to easterly winds were prevalent. It was generally fairly breezy too, accentuating the cool feel.

Measure	Unit	Minimum	Average	Maximum	Average min	Average max	Total
Relative humidity	%	48	77	95
Temperature	°C	4.3	12.5	21.6	8.1	17.7
Wind source (most common/highest gust)	Sector		N	E
Wind speed	mph		2.7	21		15.4
Rain daily accumulation	mm		1.1	22.4			34.8
Barometric pressure	hPa	1007.7	1021.8	1031.7
Solar irradiance during daylight	W/m²		287	1239		897
Sunshine (sunny if irradiance > 120 W/m2)	Hours		10.8	12.5			333.5