The averaging period used for the following assessment was 1961-1990.
A very wet month in most places, with some areas over England & Wales receiving over double the average May rainfall. The NE of Scotland was the exception, seeing close to average rainfall. Mean temperatures ranging from close to average across Northern Scotland to well above average across East Anglia. Sunshine ranging from well above average across Shetland to below average across Southern England.
Northolt and central London recorded a maximum temperature of 27.7 °C on the 4th. Lerwick recorded 75.6 hours of sunshine in the six-day period 21st-26th.
England and Wales diary of highlights
A wet month, especially across East Anglia and parts of Wales where over twice the average rainfall was recorded in some places. Notably warm at times during the first half of the month, but much cooler during the closing days with some overnight ground frost. Some significant thunderstorms, especially in the south on the 10th. Windy with coastal gales early in the second half of the month.
1st to 5th: The first couple of days of the month were characterised by low pressure to the north-west of the UK, bringing a period of rain to many parts followed by bright and showery conditions. Pressure then began to build across the south, allowing a largely dry and settled spell of weather to develop. With winds blowing from a southerly direction, it became increasingly warm. Central London recorded a maximum of 28 °C on the 4th, notable for early May.
6th to 9th: An Atlantic low pressure system drifted across the south of the UK, bring a further spell of wet weather with occasional thunderstorms. Some notable rainfall totals were reported. Manston (Kent) recorded 20 mm in the 12 hours to 10 p.m. on the 6th. As the rain band settled across the east of the UK, further notable rainfall totals were recorded at Holbeach (Lincolnshire) and Wattisham (Suffolk), 40 mm and 34 mm respectively.
10th to 12th: Pressure once again increased across much of the UK bringing plenty of dry, sunny and warm weather. However, the warm weather triggered some thunderstorms, most significant on the 10th when an organised cluster of storms developed across Oxfordshire, Berkshire and Hampshire and drifted slowly west. Frequent lightning and hail were reported. Coastal fog was also a feature in the south-west, and on the 10th limited the temperature at Camborne (Cornwall) to just 11 °C while a sunny Southampton recorded 24 °C. A thundery shower gave Hawarden (Flintshire) 29 mm of rain on the 12th.
13th to 16th: Generally turning cooler and unsettled, with a mixture of sunny spells and showers. Some of the showers were heavy and thundery, particularly on the 13th when Pershore (Worcestershire) recorded 22 mm in the 12 hours to 10 PM.
17th to 22nd: A succession of Atlantic low pressure systems gave a decidedly unsettled period of weather to England and Wales. Heavy rain fell across many areas, locally thundery, while winds became strong at times with coastal gales. The rain was particularly heavy across the Welsh hills and mountains, with Capel Curig recording 37 mm on the 17th. Notable gusts during this period included 55 knots at Mumbles (Swansea) on the 18th and 58 knots at Lee-on-Solent (Hampshire). Temperatures were disappointingly cool.
23rd to 31st: The first few days saw weather fronts spreading in from the west to bring further spells of rain. However, at least the strong winds began to abate. Wales and western England saw the lion's share of the rain, with Pembrey Sands (Carmarthenshire), Trawscoed (Ceredigion) and Buxton (Derbyshire) all recording 25 mm or more. The final days of the month saw pressure rising from the west, allowing the weather to become more settled across Wales and the west of England. However, eastern areas were affected by heavy showers, locally thundery with some hail, and a cool northerly wind. Parts of East Anglia ended the month on a cold note, with just 10 °C recorded at Cromer (Norfolk) on the 31st. Some inland areas suffered overnight ground frost.
Scotland diary of highlights
Cool and unsettled apart from warm spell early in month..
May began on an unsettled note with Atlantic depressions pushing fronts northeast across Scotland, bringing periods of rain, especially to the north-west.
From the 4th to the 11th the main centre of low pressure transferred south from Iceland towards the Azores while an anticyclone over Scandinavia moved slowly west to Greenland. Winds over Scotland gradually backed from south to east and once warm air arrived on the 4th, it persisted throughout the period. It was unsettled at first with the Atlantic depressions pushing fronts across Scotland. On the 4th the Hebrides and west coast experienced severe thunderstorms, highly unusual for this part of the world at any time, let alone early May. Later the northern anticyclone took control, bringing sunny weather to all parts with the temperature reaching 24 °C somewhere in Scotland every day between the 8th and 11th.
On the 12th a cold front moved slowly south across Scotland, introducing a dramatic drop in temperature. At Aboyne the maximum was 8 °C and during the following night -4 °C was recorded in Highland glens. Mostly fair weather on the 13th was replaced by cloud and rain on the 14th and 15th as Atlantic depressions pushed fronts north across Scotland.
Unsettled weather continued between the 16th and 19th but winds turned into the south-west and it was much milder than before, especially at night. On the 17th the minimum temperature at Prestwick was 12 °C.
From the 20th to the 29th the main centre of low pressure lay to the east of Iceland and the changeable weather continued, but the air circulating around the low was cold. On the 20th the maximum temperature at Carterhouse was 9 °C and on the 23rd the minimum temperature at Tulloch Bridge was -4 °C. It was often windy with gust of 51 knots at Charterhall on the 24th. Bands of rain affected the country on the 22nd and 26th but showery conditions predominated and there was much bright weather. Lerwick recorded 76 hours of sun between the 21st and 26th. A ridge of high pressure brought fair weather to most districts on the 30th and 31st.
Northern Ireland diary of highlights
A warm second week - otherwise often rather cool and wet - notably so in the third week.
The opening day of the month, coinciding with the May-Day holiday was bright with some sunny spells and just a few light showers. Gusty north-west winds eased through the day but it felt cool with temperatures no higher than 13 °C. This was followed by a very windy day on the 2nd with coastal gales in the east and rain spreading eastwards, which gave 10-15 mm in places. The evening was brighter with scattered heavy showers. The unsettled theme continued on the 3rd and after a dry, bright start rain, some locally heavy spread eastwards in the afternoon.
The 4th brought some dramatic weather with heavy, thundery rain in the east and this was briefly torrential in places. 180 lightning strikes affected the electricity network with east Antrim and Down worst affected and some 10,000 homes were without power at some point in the day. Rainfall totals were around 10 mm in the east, falling in just an hour or two during the afternoon in some areas.
The 5th to 7th saw an improvement generally with some sunshine and just a scattering of showers. Temperatures by this time had recovered to the mid-teens.
The 8th dawned cloudy with some showery rain, locally heavy but the afternoon became drier and much warmer with some sunshine and temperatures lifted to 21 °C in places.
Much of the second week was then sunny and warm and the rise in temperatures continued with a maximum temperature of 24.0 °C at Derrylin in Co. Fermanagh on the 11th - the month's highest reading. Many areas enjoyed very sunny conditions with daily totals of 12 or 13 hours. The heat on the 11th set of some heavy and thundery showers in the evening and these rumbled on into the morning of the 12th though rainfall totals were not significant. Once this cleared the remainder of the 12th and 13th were mostly dry and sunny though cooler with highs 14 to 17 °C.
The third week saw the establishment of much more unsettled conditions and low pressure brought showers or longer spells of rain to many areas between the 14th and 21st. Some of the rainfall was heavy and thundery with 50 mm of rain widely in the week and locally 70 mm at Silent valley or nearly 4 times the weekly average. The 21st was particularly grim with heavy afternoon rain and temperatures struggling near 6 °C.
The 22nd and 23rd brightened up with scattered showers but it was very much cooler with ground frost and even some local air frost at night. The minimum of -2.5 °C at Katesbridge in Co. Down on the morning of the 23rd was the lowest of the month. The last week continued unsettled with further rain or showers in many areas and overnight rain on the 25 / 26th gave a further 10-15 mm in some areas, adding to what now was a very wet month generally. The last few days saw high pressure building to the west of Ireland but a strong and gusty north to north-west wind made it feel particularly cool despite temperatures in the mid-teens. The last day of the month was warmer with lighter winds and temperatures between 16 and 18 °C.