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May 2011

The averaging period used for the following assessment was 1971–2000.

UK overview

With areas of low pressure to the north or west of the UK for much of the month, the weather was often cloudy and at times windy. There was also copious rainfall over north–western areas, although very little reached the south–east. The UK mean temperature was 1.0 °C above the 1971–2000 average. It was a very wet month across western and northern Scotland, with well over 200% of the average recorded. In sharp contrast, it was very dry over much of East Anglia and south–east England where less than 30% of normal rainfall was recorded; the third successive very dry month in these areas. In series from 1910, it was the wettest May on record in Scotland but among the driest on record in Essex and Kent. It was a rather dull month across western areas, but sunshine amounts were somewhat above normal over eastern England and eastern Scotland.

A maximum temperature of 25.4 °C was recorded at Weybourne (Norfolk) on the 7th. A minimum temperature of -6.3 °C was recorded at Altnaharra (Highland) early on 4th. In the 24 hours ending at 0900 on the 22nd, 92.4 mm of rainfall was recorded at Alltdearg House, near Sligachan, Isle of Skye. In marked contrast, a few places in Kent and East Anglia recorded only about 10 mm of rain in the whole month. A wind gust of 84 m.p.h. was recorded at Blackford Hill, Edinburgh on the 23rd.

England diary of highlights

After a fine, warm start, it was a generally changeable month with westerly airstreams bringing plenty of cloud. Any showers or periods of rain mainly affected areas towards the north and west, whereas the south–east stayed largely dry. The mean temperature for the month was 1.3 °C above the 1971–2000 average. It was a wet month over Cumbria, with over 150% of normal rainfall, but much drier than normal in eastern and southern counties. It was particularly dry over much of East Anglia and south–east England, with less than a third of the normal amount; Essex and Kent had one of the driest Mays on record. Sunshine amounts were close to, or a little below normal towards the west coast, but it was sunnier than normal across eastern England.

1st to 4th
An easterly then south–easterly air flow gave a generally fine and settled start to the month. In the west, occasional showers gave around 10 mm in parts of Cornwall on 1st, and the south–west caught the majority of the showers through to 4th. It was windy at times, especially on 1st and 2nd. Early on 4th, temperatures fell close to or below freezing, especially in sheltered inland areas with values as low as -3.0 °C in places.
5th to 10th
A slow–moving area of low pressure lay over the near–Atlantic, bringing unsettled conditions into western areas in particular, with generally south–westerly winds. Pulses of rain affected western England at times on 5th, with heavy and thundery showers moving northwards on 6th and 7th. Temperatures climbed, particularly in the east, where 25.3 °C was recorded at St James’s Park (London) on 6th and 25.4 °C at Weybourne (Norfolk) on 7th. Over these two days, 20 to 30 mm of rain were recorded across a broad swathe of central England, but amounts were much lower further east. Sunshine and showers was then the theme for the remainder of the period, with the showers generally spreading from eastwards.
11th to 20th
High pressure over the mid–Atlantic brought a generally westerly flow, with the north–west seeing the most unsettled conditions and the south and east staying largely dry. Maximum temperatures were close to or somewhat above normal, reaching 20 °C in the south–east on 18th and 19th.
21st to 27th
A series of deep low pressure systems passed north–eastwards over the UK, bringing unseasonably strong winds for a time. These were separated by quieter, drier interludes. On 22nd, persistent rain gave more than 20 mm in parts of Cumbria, whereas most of the south–east saw very little rain. The 22nd and 23rd saw strong winds across much of England, particularly over the Pennines, with 55 m.p.h. gusts here. Winds then eased, with mainly dry weather and some chilly nights. By 26th, showery conditions gave heavy rain in places, including the south–east. Both 26th and 27th were a little cooler, with daytime maxima around 17 °C.
28th to 31st
The southern half of England was cloudy with a little light rain and drizzle at times, a front moving south–eastwards on 30th. This was followed by high pressure building from the south–west on 31st, giving a chilly night across the south under clear skies and a local ground frost.

Wales diary of highlights

After a dry and sunny first few days, the weather was unsettled with rain or showers and it was windy at times. The mean temperature for the month was 0.9 °C above the 1971–2000 average. Rainfall was about 30% above normal in Anglesey and Snowdonia but mostly nearer normal elsewhere. It was a dull month, particularly towards the north and west.

1st to 4th
The month got off to a dry start with warm, sunny spells across the north, although high cloud affected southern parts. There was also a strong easterly wind for a time on 1st and 2nd, with gales over the hills. However, the direction of the wind lead to some warm weather in the north–west, Porthmadog (Gwynedd) recording 21.2 °C on 1st.
5th to 13th
Much more unsettled conditions took over as a large, complex area of low pressure became slow–moving to the west or south–west of Ireland from 5th to 9th, then transferred north–eastwards. Areas of rain and showers moved in from the south and west at times, often heavy and thundery, especially up to 10th. On 9th, the showers turned very heavy with frequent lightning and hail reported. A further period of heavy, thundery rain moved across on 13th, clearing to showers behind. Some chilly nights, but temperatures were near normal by day.
14th to 21st
High pressure built in across southern parts of the UK at times but low–pressure areas continued to track eastwards to the north and north–west. This brought a good deal of dry weather for much of Wales, especially the south, with some sunshine. However, areas of cloud and rain crossed all areas at times, especially in the north on 21st. Under light winds and clear skies, there were some chilly nights, with just 0.6 °C at Sennybridge (Powys) early on 19th, and widely near 2 °C. Daytime temperatures were generally near or above normal.
22nd to 26th
Becoming even more unsettled as Atlantic low–pressure areas tracked eastwards bringing unseasonably windy weather, along with periods of heavy rain and thunderstorms. One of the wettest and windiest days was 23rd, with gusts in excess of 65 m.p.h. and 20 mm rainfall over the mountains. After a brief respite on 24th, a further deepening low moved eastwards on 25th and 26th, bringing heavy rain, thunderstorms and further strong winds. Temperatures were near or rather below normal.
27th to 31st
The weather continued to be unsettled but pressure tended to be higher across southern areas. This meant any rain tended to be lighter, with lengthier dry spells in between. However, 30th was rather wet through the morning, clearing to showers in the afternoon. Temperatures, still on the cool side at first, recovered to normal.

Scotland diary of highlights

After a dry and sunny first few days, the weather was unsettled with rain or showers and some strong winds at times. The mean temperature for the month was 0.7 °C above the 1971–2000 average. Rainfall was well above normal across most areas and it was particularly wet in the west and north, where well over twice the normal amount was recorded. Some stations here had a record wet May; at Stornoway airport it was the wettest in an 80–year series. It was the wettest May generally across Scotland, in a series from 1910. It was a dull month along the west coast, but somewhat sunnier than normal towards the east.

1st to 4th
The month began with mostly dry weather and some long spells of sunshine. Despite a cold start to 1st, with the temperature falling to -4.9 °C at Braemar (Aberdeenshire), sunshine lifted temperatures and Kinlochewe (Highland) recorded a high of 20.6 °C. Parts of the east coast were affected by haar on 1st and early on 2nd, otherwise it was also sunny here. The 3rd and 4th continued this fine spell, with frosty nights and warm, sunny days.
5th to 20th
Cool, rainy weather spread northwards to all areas on 5th. Showery outbreaks of rain early and late on 6th, with some sunshine during the afternoon. The 7th was mainly cloudy with showery outbreaks of rain, thundery in places. Brighter weather in the north–west lifted the temperature to 22.7 °C at Lusa (Skye). The 8th and 9th had sunshine and thundery showers, giving 32.4 mm at Braemar on 8th. Rain spread north–eastwards on 10th, followed by sunny spells and occasional showers. The period 11th to 14th was bright with sunny or clear spells and occasional heavy showers, thundery in places. The 15th and 16th were cloudy with rain at times, heaviest in the north–west. From the 17th to 19th it was bright and showery, the showers more frequent and heaviest in the north and west. It was also windy, reaching strong to gale force in the north. Heavy rain at first on 20th, then brighter with showers, frequent over western areas and some heavy and thundery.
21st to 31st
The 21st was dull and wet in most places, through drier in the north–east. The heaviest rain was over the west Highlands, where totals of over 25 mm were widely recorded each day from 19th to 23rd. The 22nd was a bright, blustery day with sunshine and showers. The 23rd started very wet with Eskdalemuir (Dumfries and Galloway) recording 38.6 mm of rain in the morning, before the rain cleared to blustery showers. Severe gales became widespread causing disruption to transport and power lines, with reports of fallen trees in many areas. At Drumalbin (South Lanarkshire) a gust to 77 m.p.h. was recorded, and one of 84 m.p.h. occurred at Blackford Hill, Edinburgh. It was bright and breezy on 24th with occasional showers, but more frequent in the north–west. Starting bright in the east on 25th but cloud and rain spread northwards and eastwards to all parts. Cloudy with outbreaks of rain on 26th but brighter showery conditions spread into the west later. The rather cloudy conditions continued on 27th with showers or spells of rain. Rain soon cleared on 28th then it was bright and breezy with scattered showers, isolated in the east. The 29th followed a similar sequence but with gales in the afternoon, Blackford Hill (Edinburgh) recording a gust of 60 m.p.h. Lighter winds and a mixture of sunshine and heavy showers to end the month, although more persistent rain spread into the west during the evening of 31st.

Northern Ireland diary of highlights

After a dry and sunny first few days, the weather was unsettled with rain or showers and it was windy at times. The mean temperature for the month was 0.8 °C above the 1971–2000 average, associated with near–normal daily maxima but night minima 1.7 °C warmer than average. Rainfall was generally above normal, particularly to the west where over 200% of average was recorded. Sunshine amounts were close to normal, but it was a rather dull month in the west.

1st to 4th
The month started on a promising note, with dry and sunny weather for the first four days. It was quite warm, especially on 1st and 2nd. Cloud thickened late on 4th with some rain reaching the west in the evening.
5th to 21st
The rain lasted well into 5th before it gradually dried up in the afternoon. The 6th started bright before more showery rain spread in during the afternoon. The 7th was also changeable with bright spells and showers or longer spells of rain, though it was quite warm, 19.2 °C being achieved at Ballykelly (County Londonderry). The 8th and 9th were bright with sunshine and heavy showers, some thundery. Outbreaks of rain spread eastwards overnight into 10th, clearing soon after dawn to leave sunny spells and occasional showers. From 11th to 14th it was bright with a mixture of sunshine and showers, some of the showers locally heavy with thunder. The 15th and 16th were mostly cloudy with outbreaks of mainly light rain. Cloudy but mild on 17th, with some bright spells in the east late in the day, lifting temperatures at Killowen (County Down) to 18.0 °C. The 18th and 19th were bright with some showers, but also rather breezy. Rain early on 20th quickly cleared, followed by bright weather and scattered showers. The 21st was cloudy with rain, this becoming very heavy in parts of the east in the evening, Portglenone (County Antrim) recording 14.6 mm in 1 hour.
22nd to 31st
The 22nd was bright and blustery with showers. Rain overnight cleared to blustery showers on the 23rd. Severe gales were widespread causing disruption to power and transport, Castlederg (County Tyrone) recording a gust of 76 m.p.h. and Orlock Head (County Down) 79 m.p.h. It was a bright and breezy day on 24th with scattered showers but cloudier on 25th with showers or longer spells of rain. Rain at first on 26th, then turning brighter with some showers. These continued into 27th before it turned cloudy with some light rain spreading in later. The rain soon cleared on 28th, then it was bright with sunshine and showers over the next few days, with gales in the north on 29th and patchy light rain across the north and west through the evening of 31st.


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