The averaging period used for the following assessment was 1961-1990.
Temperatures above average across the whole of the UK, with near or above normal sunshine across most areas. Much of the UK was wetter than average, with only parts of the north and east experiencing less than normal rainfall.
Temperatures peaked at a high of 28.5 °C on Jersey on the 16th, and fell to a low of -5 °C at Corgarff on the 6th. Hail showers over Belfast on the 27th, led to ground surface accumulations of up to half an inch.
England and Wales diary of highlights
Chilly at first, with some overnight frost and scattered showers. More unsettled later with a short heatwave mid month. Wet and windy, with thundery showers for the end of the month.
1st to 12th A changeable, but mostly dry period. Counties bordering the North Sea were affected by hill and coastal fog at times later in the period, from about the 8th to the 12th. It was chilly generally, with slight frost at night from time to time. However most places saw sunny periods, in particular Wales and western areas, which had the best exposure. There were scattered showers in the first few days, some with thunder, 25 mm falling at Keston (Kent) on the 3rd. Vigorous low pressure developed over the western Mediterranean by the 7th and with rising pressure over Scandinavia, an easterly drift became established by the 6th. There was some patchy light rain or drizzle in east and south-east areas from the 5th to the 7th and some thundery rain in northern England on the 7th. Low pressure moved to the east by 10th, producing slack gradients and scattered showers by the 11th and 12th. Shap (Cumbria) recorded -1.9 °C early on the 12th.
13th to 14th An Atlantic low moved north-east passing Ireland and Scotland and associated fronts brought wind and rain, with gales at times around western coasts. The rain was heavy in places at first, however by the 14th scattered blustery showers were the order of the day.
15th to 17th An anticyclone over Europe brought a short-lived spell of hot weather especially on the 16th, when Jersey peaked at 28.5 °C. Thundery rain, sometimes heavy, affected southern districts the next day.
18th to 26th With vigorous low pressure close by over the Atlantic, the weather became very unsettled. There were frequent outbreaks of blustery rain and showers, some heavy with hail and thunder at times especially in the west. The 24th and 25th were particularly windy with gales around coasts and a number of reports of gusts to 57 knots. However, the sun did manage to shine between the bands of rain and showers. The 26th was cooler and quieter but more thundery rain still affected a number of places. In the Haywards Heath (West Sussex) area a farmer reported a damaging tornado which killed one of his cows with flying debris.
27th to 31st Low pressure to the north-west continued the unsettled theme up to the 30th with rain and scattered showers, again some were heavy with hail and thunder in quite a few places. On the 31st a ridge extended from the continent bringing some warmer, sunnier and drier weather for the last day.
Scotland diary of highlights
A fine start followed by an unsettled regime.
High pressure dominated the first 12 days of May, giving rise to much dry and sunny weather, with some cold nights and warm days. The remainder of the month was cyclonic southerly, with bands of rain being separated by showery interludes.
A cold and unstable Arctic airmass covered Scotland during the first two days of May, giving sunny periods and showers. On the 2nd the temperature at Corgarff fell to -2.3 °C and hail 4 cm in diameter fell at Wishaw.
On the 3rd a ridge of high pressure moved into Scotland from the west and remained over the country until the 7th. The weather was mostly sunny, with a large diurnal range of temperature superimposed on a warming trend. Cold nights at first led to Dalwhinnie recording -3.4 °C on the 6th, while warm days culminated in 22.1 °C at Dalmally on the 7th.
By the 8th and 9th the high pressure had retreated to the north, with easterly winds developing across Scotland. Fair weather prevailed, but there was more cloud in the east and a trough brought some rain to the south overnight on 7th/8th.
Low pressure transferred rapidly from the Netherlands to the Faeroes on the 10th, giving a cloudy day with some rain, but mainly sunny weather was resumed in a clear and cold westerly during the next couple of days.
The remainder of the month was unsettled with the main axis of low pressure over the Atlantic and individual depressions moving north over or to the west of Britain. The weather was predominantly showery, but there were regular bands of rain crossing the country. Winds were between south-east and south-west so that rainfall amounts were largest in the south and south-west.
Variations on the theme occurred on the 16th, when warm air from the south enabled the temperature at Prestwick to reach 21.3 °C. Drier air on the 21st gave a mainly fair day, especially in the north where Durness recorded 20.7 °C.
Northern Ireland diary of highlights
This was a wet May with monthly rainfall totals typically between one and a half and two and a half times normal in all areas of the province. Conditions were however mild, with both day and night-time temperatures above average. In terms of sunshine, conditions were very much as could be expected for the time of year, with values close to average in all areas.
1st to 11th Mainly dry, with only occasional showers or spells of rain. Conditions were also very sunny with daily sunshine durations in double figures in many areas from the 2nd through until the 6th. A passing frontal system did however give dull conditions on the 7th and 8th. The period 1st to 4th was the coolest of the month, with both day and night-time temperatures below average for the time of year. Ground frosts were recorded in many areas from the 2nd to 5th, while an air frost was also reported in isolated locations on the 4th.
12th to 15th Unsettled with bands of rain closely pursued by scattered showers and sunny spells. Good spells of sunshine between showers gave a sunny day in many areas on the 14th.
16th to 17th The 16th proved the warmest day of the month in many areas, with maximum temperatures of up to 21 °C recorded on this date. Thunderstorms, heavy showers and longer spells of often heavy rain overnight on the 16th/17th and through much of the day of the 17th, made this the wettest spell of the month, with over 50 mm of rainfall recorded in parts of County Down during this period. Western areas however escaped the worst of this weather.
18th to 26th Unsettled with bands of rain and frequent and often quite heavy showers throughout the province. The period 21st to 24th was wettest with many areas recording rainfall totals in double figures on all of these dates. Indeed parts of County Down recorded more than 50 mm of precipitation from the 21st until the 23rd, while in parts of Belfast more than 25 mm of precipitation were recorded on the 21st alone.
27th to 31st Very unsettled, with heavy showers and thunderstorms recorded across the province. Parts of Belfast recorded hail showers on the 27th, which lead to accumulations of up to 12 mm of solid precipitation over ground surfaces.