UK weather latest: Temperatures to shoot up before electrical storms strike later this week

Soaring mercury to bring thundery showers on Thursday and Friday

Temperatures across the British Isles are set to soar well above average this week, before bursting into thunder, lightning and rain late on Thursday.

Wednesday will see the fresher weather and white skies of the first half of the week replaced by a firmament of dazzling blue and powerful sunshine in most areas. Temperatures will rise into the twenties, with some parts of the southeast experiencing highs of 25C, forecasters said.

But by Thursday warm air creeping across the English Channel from France will see more cloud begin to billow up the country, creating more humid air.

“We’ve had a lot of thundery weather across Europe for the last four or five days, and that will start to edge its way into the southern UK in the second half of Thursday,” Met Office meteorologist Simon Partridge told The Independent.

He added: “In the afternoon there’s the potential to see some heavy thundery showers anywhere across the southern third of the UK.”

This could bring dangerous travel conditions on some roads, he warned.

“There’s potential we could see some localised surface water problems – surface water on major roads, which could bring hazardous spray for drivers. Potentially some very localised flooding – details of which we will have to look at closer to the time. That’s from Thursday afternoon through to the evening.”

On Friday the outlook is similar with high temperatures well above average for the time of year, along with tropical humidity and the potential for outbreaks of thunder and lightning.

“That warmer air edges its way further northwards and then we’re looking at the risk of thundery showers in the afternoon once things warm up a touch – this will affect areas from the Pennines southwards, and there’ll be a bit more cloud around,” Mr Partridge said.

The return of the hot weather follows a week of unusually high temperatures which saw May smash records for heat.

Provisional Met Office statistics gave an average maximum temperature of 17C, making it the warmest May since 1910, and beating 1992’s 16.9C.

Though temperatures are above average, there will be too much cloud to see more records broken this week, Mr Partridge said.

“Average maximum temperatures for London at the moment should be around 19 degrees, but we’re going to be seeing around 26C later this week – well above average,” he said.

Despite the soaring mercury, many coastal areas have been swaddled in haar – sea fog. Though most parts of Britain will see improving weather on Wednesday, the haar is forecast to roll in to cover the northeast coast of England and the southeast coast of Scotland, Mr Patridge warned.

“Haar is a problem as water temperatures remain cool –as low as 10 degrees even in some southern areas,” he said.

Speaking about recent sea fog on the south coast, he added: “We have this warm humid air across the continent, and as that moves across the English Channel the fact that the water is that bit cooler than the land, cools the air and it condenses into mist.

“It’s common at this time of year with land temperatures being that bit warmer than the sea.”