May weather

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One expects May to be a month of pleasant weather and gentle temperatures, but in fact it can be a very mixed month, with quite substantial fluctuations.

The month ought to be like 2011, 2018 and 2020, when it was largely sunny, but more often than not it sees quite a bit of drab, grey conditions. A mixture of slow-moving areas of high and low pressure often bring these conditions. Lows obviously bring cloud and cooler conditions, but highs do not always result in sunshine either.

Much depends on where the high is situated and whether it brings in air from the warmer south and west or cooler east and north. With the sea still cold, any airflow coming over the sea also tends to create cool grey cloud, often bubbling up after sunny starts and then clearing at dusk.

From cold to hot and back again

A typically mixed May in recent years was 2024, when slow-moving highs and lows battled for dominance. After four particularly cloudy months, 7 to 12 May finally produced the right kind of high pressure, with six continuous days of hot sunshine and temperatures of up to 26 degrees. But lurking lows kept the weather mostly cloudy and sometimes wet for the rest of the month, with temperatures largely in the mid to upper teens. Two brief exceptions were a sunny 19th and 20th of the month, and sun and cloud on the 24th and 25th.

2022 saw a similar tussle between slow-moving highs and lows, with no clear weather pattern emerging. The last eighteen days of April had been dry, leaving the countryside looking a bit tired, but May reversed this, with 13 days having some rain, and one or two thoroughly wet. On the other hand there also seven fully sunny days, and some sunshine on twelve other days. Maximum temperatures were in the high teens or low twenties, which felt hot or a little cool, depending on the direction of the wind and the amount of cloud cover.

In 2023 the month started unsettled, with sunshine, cloud and showers, the worst day of all being 6 May, when the coronation of King Charles saw steady rain. This followed on from a March and April that had both seen twice the usual amount of rainfall in the south east. High pressure centred to the north, west or south west then set in from the 12th, resulting in north easterly winds which pulled in cloud from the North Sea overnight. This burned back to sunshine from the south and west in varying degrees by day, while the west of England and Wales enjoyed almost continual sunshine. Temperatures in the south east were moderated by the breeze, reaching mostly just into the high teens, but as high as 22 degrees on the 28 May. By early June the countryside was starting to look parched.

In 2019 the month started with high pressure to the west, causing a north easterly airflow, followed by four days of slow-moving lows. High pressure then set in over the UK, bringing sunny days and temperatures of up to 21 degrees from the 12th to the 16th. There were then four days of cloud before another high set in from 21 to 25 May, bringing some days of hot sun, with temperatures of 24 degrees on 23 May, but also two cloudy ones. The month then ended with westerly lows. In all there were eight sunny days in the month, with some sun on another fifteen, but with rain on ten days.

In 2017 the month started with high pressure to the north, producing an easterly wind of the North Sea. Then from the 11th onwards static lows dominated till the 21st. This meant that the first three weeks were fairly cloudy, though with relatively little rain apart from the 18th and 19th. But then from the 22nd onwards a continental high brought a heatwave, with hot sunshine and temperatures up to 28 degrees

May 2016 was another month of alternating highs and lows, but saw good amounts of blue sky (twelve sunny days, six of sun and cloud), with cloudier, wetter periods from 10-11, 17-22 and 29-31 May. Temperatures were in the high teens, with a brief foray into the mid twenties on 6-9 May - a welcome change to the end of April, when there had been a week of wintry north winds with highs of only 9 degrees. Towards the end of the month a static low set in over the near continent that was to bring cool cloud to the south east in early June while Scotland basked in hot sunshine.

Better years include 2020, the sunniest May on record. Following on from a largely dry April, this produced the driest spring (calendar March to May) in 124 years, somewhat inevitably coinciding with a nationwide lockdown due to the Covid pandemic. There were 15 days of full sunshine - from the 6th to the 9th, 18th to the 21st and 25th to the 31st - in each case pushing temperatures into the mid 20s (28 degrees on the 20th). There was only minimal rain and by the month's end the countryside was becoming parched.

In 2018 highs - centred south west or north east of the UK, or later over Scandinavia - dominated nearly the whole month, the exception being westerlies in the first two days of the month, and the second week, which saw slow-moving lows. There was fine weather throughout the month, with 15 full sun days and nine of sunshine and clouds: only seven days had no sun at all. Ten days saw rain, but on five of these the rain fell overnight.

Years when May was wet

More unusually, May can be dominated by Atlantic lows. An example was 2021, a thoroughly wet May after a very dry April. The month saw very slow moving lows in charge from the 3rd to the 25th, with rain on 21 of the first 25 days of the month. This included two big storms (on 3-4 and 20-21 May), but otherwise the rain came in the form of heavy showers. In the last six days of the month high pressure finally established itself, bringing fine weather and temperatures into the low twenties just in time for the late May bank holiday.

In 2012 the weather remained stubbornly cold and wet, with temperatures as low as 9 degrees early in the month, and the ground as sodden as in winter. Then in the last eight days of the month there was a complete change, with high pressure, sunshine and temperatures of 27 degrees. 2006 and 2007 were also famously grey, cool and wet Mays, the former the wettest May for 23 years.

In 2011 a hot drought that had lasted since late March and brought summer temperatures finally ended on 7 May with heavy downpours. The month then reverted to sunshine, however, with a mixture of static highs and lows. These produced much cooler and breezier conditions than in April, with temperatures mainly in the high teens, but there were only isolated and light showers for much of the month. Then just when the drought seemed to be setting in for the summer, there was substantial rain across the south east on the 26th, and more on the 30th and 31st, with the month ending on a cool, grey note.

Lighter clothes at last

Generally, even if the weather is not cooperative, coolness in May is relative – in March similar temperatures would have seemed balmy and warm. Winds do not tend to be cutting. It can still be cold enough for an extra layer, but only one: this is the first month when one can go out for the day relatively lightly dressed.

When the weather is sunny, the outside tables of a pub or cafe are suddenly all occupied and the inside ones empty – the exact reverse of the situation for the previous six months. People start to stand around drinking outside city pubs, Towards the end of the month one starts feeling the need to use suntan cream for the first time and even to sit under the shade of trees. Generally it no longer gets sharply colder in the evening - temperatures typically are 9 to 10 degrees at night.

Almost unnoticed, you are in the some of the longest days of the year. Lighting up time goes from 8.30pm to 9.05 pm during the month, but it barely seems to register, and one rarely seems to make the best of the extra daylight.

Bank holiday weather

May has two bank holiday weekends and it is almost inevitable they will include some unsettled weather. In theory one might expect the later one to have better weather than the early one, but in fact there seems to be no difference. The Mondays have a particular tendency to be disappointing.

Good years for the early May bank holiday weekend include 2014 and 2018, when it was sunny throughout (with temperatures of 25 degrees in 2018, rising to 29 degrees on the Monday), while in 2013 after an unsettled start to the Saturday the rest of the weekend was sunny, apart from a few areas of stubborn static cloud.

In 2021 and 2024 there was largely fine weather on the Saturday and Sunday, but wet weather on the Monday. In 2019 Saturday was sunny, though with a chilly breeze, with the Sunday and Monday cloudy - the coldest May bank holiday Monday ever, in fact, with temperatures of just 11 degrees by day and 2 degrees overnight. 2022 saw a sunny Saturday followed by two cloudy days too, though the Sunday and Monday were nothing like as cold as in 2019.

In 2020 the weekend that would have been the bank holiday saw sun and cloud, but it was moved to the following Friday, 8 May, to commemorate the 75th anniversary of VE Day (a celebration that was scotched by the Covid lockdown): that weekend saw a hot Friday and Saturday followed by a cooler, cloudier Monday.

In 2023 the traditional bank holiday was reasonably fine, if rather cloudy on the Monday, but a special bank holiday weekend for the coronation of King Charles the following weekend saw persistent rain on coronation day itself, cloud for most of the Sunday and cloud with evening rain on the Monday.

As for the late May bank holiday weekend, in 2013 there were blue skies throughout, making this a rare year when both bank holiday weekends in May were sunny. 2021 and 2023 were also mostly sunny, while in 2018 morning cloud, afternoon sun and evening rain on the Monday followed perfect blue skies on the Saturday and Sunday.

In 2019 the Sunday was sunny and warm, but Saturday and Monday saw some cloud and isolated showers. In 2020 the Saturday saw heavy showers in Sussex and the southern part of Kent, followed by a cloudy Sunday and then hot sunshine on the Monday. In 2024 there was sun and cloud on the Saturday, but somewhat showery weather on the Sunday and Monday

In 2012 there was no late May bank holiday due to the Queen's Diamond Jubilee celebrations the following weekend, but had it been in its usual place, it would have been hot and sunny. The four day Jubilee break at the start of June, by contrast, saw two days of heavy rain and was generally rather grey and cool.

In 2022 shifting the holiday for the Queen's Platinum Jubilee had little effect, however: the weekend that would have been the late May bank holiday saw some sunshine but a lot of cloud, and that was largely true for the four day Jubilee break too.

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