The averaging period used for the following assessment was 1971-2000.
The first three weeks were dominated by cool and, at times, unsettled conditions - continuing the wet theme of much of April. A marked improvement occurred from 21st, with a much warmer and more settled spell. Temperatures rose above 27 °C at least somewhere in the UK each day from the 23rd to the 28th. With prolonged sunshine, it was particularly warm across Highland Scotland, and a new May temperature record for Scotland was set on 25th.
The UK mean temperature was 0.5 °C above the 1971-2000 average, the very warm spell towards the end of the month offsetting the earlier cool conditions. The rainfall pattern was variable, but totals in many areas were near average. However, it was drier than normal across much of south-west and central-southern England, and wetter than usual in parts of Scotland, northern England and Suffolk. Apart from south-east England, May was somewhat sunnier than average, notably across northern Scotland where, provisionally, it was the third sunniest May on record.
A maximum temperature of 29.3 °C was recorded at Achnagart (Highland) on the 25th, a new May record for Scotland. A minimum temperature of −6.2 °C was recorded at Saughall (East Ayrshire) early on the 5th. In the 24 hours ending at 0900 on the 14th, 101.0 mm of rain fell at Kinlochewe (Highland). A wind gust of 67 mph was recorded at Blackford Hill, Edinburgh during the evening of the 13th.
Early in the month, localised flooding affected some roads and rail routes, and flood warnings were in place as rivers rose. The Badminton Horse Trials in Gloucestershire were cancelled because of waterlogged ground; due to take place in the first week, they would have served as a trial event for the London Olympics.
Overnight rain on the 2nd/3rd caused localised flooding across parts of Essex and Suffolk, with a section of the A12 closed for a time and a landslip causing train delays and cancellations between London and parts of East Anglia.
On 11th, the wet April and unsettled start to May allowed the lifting of drought orders that had been brought in across the West Midlands and South-west England in mid-April.
In sharp contrast to the mainly cool and changeable first three weeks, the last 10 days saw a run of very warm sunny days giving a welcome boost to tourism and outdoor activities including the Olympic torch relay across western England and Wales.
A cool and unsettled first three weeks, with winds mostly from the north or east. Then, a very warm and settled last 10 days, with some high temperatures for the time of year.
The mean temperature was 0.7 °C above the 1971-2000 average, the very warm spell towards the end of the month offsetting the earlier cool conditions. Rainfall amounts were generally close to normal, but ranged from about 30% below average across much of south-west and central southern England to about 30% above in Suffolk and parts of northern England. Sunshine was generally close to normal.
1st to 11th:
An unsettled start to the month with persistent and heavy rain at times. This was locally thundery in the south-east, particularly between 1st and 3rd. The 3rd was particularly cool across many eastern and southern areas, with maxima around 8 °C, and it was cool again on 5th and 6th with around 9 or 10 °C widely. The unsettled period continued with small low-pressure systems running north-eastwards giving occasionally heavy rain; 25.6 mm fell at Chivenor (Devon) on 7th. Temperatures rose to around normal.
12th to 14th:
A brief ridge of high pressure gave a more settled spell on 12th, followed by a chilly night with local air frosts in the south. A deep area of low pressure then developed to the north of the UK bringing strong westerly winds on 13th and 14th across northern parts in particular.
15th to 16th:
It was cool on 15th in a showery north-westerly air-stream. Some of these showers fell as wet snow across parts of the north-east and the Midlands, and some were thundery. There was a slight air frost in places early on 16th.
17th to 20th:
Unsettled and cool as a complex area of low pressure moved across England bringing east or north-easterly winds and spells of rain or showers. This was replaced by a weak ridge of high pressure on 20th, heralding a change of weather type for the rest of the month.
21st to 30th:
This period saw much warmer, more settled weather. Temperatures peaked above 26 or 27 °C somewhere in England on several consecutive days. These included 27.5 °C at Heathrow (Greater London) on 24th, 28.5 °C at Hurn (Dorset) on 25th, 28.4 °C at Treknow (Cornwall) on 26th, 27.7 °C at Wisley (Surrey) on 27th and 27.7 °C at Santon Downham (Norfolk) on 28th. The heat brought some heavy thunderstorms though, mainly to the south-east on 28th and for south Devon during the early hours of 27th, associated with very weak weather fronts. Humid air also brought some mist in from the sea at times to south-western and eastern areas, with some fog being slow to clear on the morning of 30th in south-east England. Overnight minimum temperatures were often around 15 °C, making it feel very sultry. Sea breezes kept coastal areas somewhat cooler.
The warm spell faded with cloud and rain moving from the west. A rather humid air mass still allowed temperatures to reach 20 °C in places across the south, but it turned cool in north-eastern areas.
The weather was unsettled and cool for the first three weeks, then drier and much warmer during the last 10 days.
The mean temperature was 0.6 °C above the 1971-2000 average, the very warm spell towards the end of the month offsetting the earlier cool conditions. Rainfall amounts were very close to normal and sunshine was somewhat above normal.
1st to 10th:
A wet and windy start to the month, with some of the rain quite heavy. On 2nd, it was cloudy, misty or foggy throughout in the east, whilst the west had some sunshine. The 3rd and 4th were further cloudy days with outbreaks of rain. There was some respite on 5th, which was mainly dry with sunny spells. The 6th was again mainly fine with sunny spells, but there were a few showers in the north. A fragmenting band of rain spread north-eastwards during 7th, with heavy and locally prolonged showers following. The 8th was dry and mostly sunny, with just an isolated shower and lighter winds, but temperatures rose only to around 13 °C in most places. On 9th, cloud and outbreaks of rain gradually spread northwards during the day. On 10th there were further outbreaks of rain and drizzle, with some heavy bursts in places, especially across the west and north.
11th to 20th:
Some respite on 11th, which was dry and fine throughout with plenty of sunshine. The 12th was another fine day with only isolated showers. After a dry and sunny morning and early afternoon on 13th, North Wales saw cloud and strong winds spread slowly southwards during the evening. The unsettled weather continued on 14th, with showers through the day, some of these quite heavy. The 15th was mostly dry and sunny, with just a few showers in the north. A mix of bright or sunny spells on 17th, but with a few showers. The 18th was a rather cloudy day with outbreaks of rain. There was more sunshine on 19th and 20th, and it stayed dry.
21st to 31st:
The weather became more settled and much warmer during this period. The 21st remained dry with plenty of sunshine. After a chilly start, 22nd was another dry, warm and sunny day with light winds. The 23rd was also fine and sunny, with temperatures rising a little higher. On 24th, early mist, fog and low cloud generally cleared through the morning, although it lingered into the afternoon in the Welsh Marches. Otherwise, it was another dry, warm day. After a mild and humid night, 25th was fine, sunny and again very warm, with Pembrey Sands (Carmarthenshire) reaching 28.2 °C. The fine, warm spell persisted through 26th, but on 27th a band of rain moved erratically northwards into south Wales, breaking up into showers. A thunderstorm occurred in Carmarthenshire, but most areas remained fine, very warm and sunny with the temperature at Porthmadog (Gwynedd) peaking at 27.9 °C. The 28th and 29th were dry and warm. After a sunny start on 30th, there was more cloud during the day than of late. On 31st, early rain cleared to leave a dry afternoon, but sea fog affected the south coast throughout. Temperatures returned to close to normal.
The weather was generally cool and unsettled during the first three weeks, with some strong winds at times. There was then a mostly dry, sunny and very warm interlude with some unusually high temperatures, particularly across Highland Scotland. Conditions turned cooler and unsettled again at month-end.
The mean temperature equalled the 1971-2000 average, the very warm spell towards the end of the month offsetting the earlier cool conditions. Rainfall was above normal in Shetland and much of north-west and south-east Scotland, with about 150% of average in the Lothians, the eastern Borders and parts of North-west Highland. Elsewhere, amounts were close to or somewhat below normal, being about 75% of normal in Aberdeenshire and the Western Isles. Sunshine amounts were above normal, especially over Northern Scotland where, provisionally, it was the third sunniest May in the series from 1929.
1st to 6th:
The 1st was generally dry with sunny spells, although rain reached extreme south-western areas during the afternoon and spread up the west coast overnight before dying out. The 2nd and 3rd were dry, sunny but cool although low cloud took time to burn off near eastern coasts. A band of rain spread southwards overnight leaving a bright day on 4th with light, scattered showers and the showery theme continued on 5th and 6th with the heaviest and most frequent showers being in the north and east.
7th to 18th:
The 7th started bright but cloud and rain spread from the south-west to reach all areas by the end of the day. This cleared northwards overnight to leave drier, brighter days on 8th and 9th with only a few light and scattered showers. The 10th saw rain spreading from the south to all areas and it was very cool with maxima typically around 7 to 9 °C. It remained wet and cool for most areas on 11th. The 12th saw an improvement with bright spells and only scattered showers for western areas. However 13th was a stormy day with strong winds and heavy rain spreading in from the north-west. There were large rainfall totals, mainly in the north where Kinlochewe (Highland) recorded 101 mm, and a gust of 67 mph was recorded at Blackford Hill (Edinburgh). The 14th saw the winds ease slightly although there were frequent showers in a cool northerly wind with thunder in Fife. A cool north-westerly wind brought further showers on 15th and 16th, these dying out later in the day. The 17th saw rain and cold easterly winds, with maxima typically around 7 to 9 °C. There was a slow improvement on 18th as the rain moved slowly eastwards.
19th to 28th:
The 19th was a drier and brighter day with only a few scattered showers in the east, and the gradual improvement continued on 20th and 21st with plenty of sunshine. The 22nd was dry, sunny and warm and 23rd was warmer still with temperatures rising close to 27 °C across parts of the Highlands and to 28.4 °C at Cromdale (Highland). The hot conditions triggered some scattered heavy showers for central areas, with Livingston (West Lothian) having a thunderstorm and 36 mm of rainfall. The period 24th to 28th remained very warm and sunny with temperatures reaching the mid to high 20s, although eastern coastal areas saw mist and low cloud during some mornings. The Scottish temperature record for May was broken on 25th when Achnagart (Highland) recorded 29.3 °C. Other high values included 27.3 °C at Bishopton (Glasgow) on 24th, 28.1 °C at Kinlochewe on 26th, 29.0 °C at Cromdale (Highland) on 27th and 26.6 °C at Aberfeldy (Perth and Kinross) on 28th.
29th to 31st:
The 29th and 30th were cloudy and some heavy showers broke out in the Borders during the late afternoon with Floors Castle (Borders) recording 19.3 mm on 30th. The 31st saw a band of rain spread from the west which cleared during the afternoon to leave showers for eastern areas.
The weather was generally cool and unsettled during the first three weeks, with some strong winds at times. The last 10 days were mostly dry, sunny and warm.
The mean temperature was 0.7 °C above the 1971-2000 average, the warm spell towards the end of the month offsetting the earlier cool conditions. Rainfall amounts were 10 to 20% below average and sunshine amounts were somewhat above normal.
1st to 12th:
The 1st was generally dry with sunny spells although the extreme south-east saw patchy rain spread from the south during the afternoon. This cleared overnight to leave cool but dry and mainly sunny days on 2nd and 3rd. A band of rain spread from the north-west during the early hours of 4th, clearing south-eastwards during the morning to leave a cooler day with a few scattered showers. These continued into 5th and 6th. The 7th saw rain spread from the south-west during the morning, clearing during the afternoon to leave some heavy showers with thunder for County Fermanagh. This unsettled theme continued on 8th and 9th with sunny spells and showers, remaining cool for the time of year. The 10th saw rain and cold winds, the heaviest of the rain for western and northern areas; 22.4 mm was recorded at Ballypatrick Forest (County Antrim). This rain cleared southwards overnight to leave a brighter day on 11th but with some scattered showers. These became fewer on 12th, with more sunshine and higher temperatures than of late.
13th to 18th:
The 13th was a wet and stormy day with rain spreading from the south-west and strong westerly winds; a gust of 56 mph was recorded at Magilligan (County Londonderry). The wind and rain abated overnight resulting in a blustery but brighter day on 14th with plenty of showers. The 15th saw a cool northerly breeze bringing frequent showers and although 16th started dry, rain spread from the west during the afternoon. This lasted for most of 17th when it remained chilly for the time of year in a north-east wind, and 18th was another cold day with patchy rain for most areas.
19th to 31st:
The 19th and 20th were dry with sunny spells and although it was cloudy on 21st it remained generally dry again. A band of patchy rain spread from the south-west during the afternoon of 22nd, clearing overnight. The period 23rd to 28th was dry, warm and sunny with temperatures readily reaching the mid-20s. On 25th the temperature reached 26.3 °C at St Angelo (County Fermanagh), the highest during this period. The 29th was cloudy but remained dry and warm, with temperatures widely reaching around 21 °C. However a band of patchy rain spread from the south-west during the morning of 30th, clearing during the late afternoon. More rain arrived during the early hours of 31st, clearing north-eastwards in the afternoon.