A 2,000-mile wide low-pressure vortex swirling off the west coast will unleash near 60mph gales and torrential downpours tonight and into tomorrow.
But it will arrive laden with steamy tropical air pushing temperatures close to 28C (82.4FF) later this week as humidity rises to 95 per cent.
The monster cyclone, named ‘Irene’ by the Portuguese meteorological service, has rapidly strengthened through ‘explosive cyclogenisis’ and is the most powerful to form in the Atlantic at this time of year since 2013, forecasters say.
Up to two inches of rain will drench parts of Britain through the next 24 hours sparking warnings for flash floods and travel disruption.
However the storm will largely be held at bay by high pressure building over France and western Germany through the coming days.
The two pressure systems will straddle the UK mid-week creating a ‘conveyor-belt’ for tropical air to sweep up from the Azores islands off the coast of Portugal.
The mercury is poised to rocket well above average for this time of year with ground temperatures of 28C (82.4F) possible in parts of the southeast by Thursday.
The UK is forecast to see record hot weather later this week
Freak weather and hot sunshine means London Marathon runners could face a steam-bath slog through the capital
Freakishly warm weather – more than 15C higher than normal for April – is tipped to hold out through the week and into the weekend.
Britons are promised lashings of sunshine and blue skies although London Marathon runners could face a steam-bath slog through the capital.
The Met Office has issued a weather warning for rain across southwest Scotland, the Lothian Borders and Strathclyde tonight.
Meteorologist John West warned to brace for strong winds in parts of western Britain through tomorrow.
He said: “We have a very deep area of low pressure out in the Atlantic which after having undergone explosive cyclogenesis will pull warm air originating from the Azores into Britain.
“It’s not all good weather for some over the next couple of days as this will bring some pretty strong winds and tricky shipping conditions.
“It is the first time we have seen a low-pressure system on this scale at this time of year since 2013 and it is quite remarkable.
“There will be some rather wet and windy weather across western Scotland tonight with further unsettled conditions in western parts over the next couple of days.”
Hot weather blast: Humidity could be 95 per cent across the UK by Wednesday
The hot weather will be sparked by Cyclone Irene, a huge churning vortex in the Atlantic
Eastern Britain will escape any effect from the storm over the next few days instead basking in warm sunshine and blue skies as temperatures rise.
High pressure will build over Europe towards the end of the week giving a boost to the plume of warm air as it engulfs the nation.
Temperatures are expected to hit 25C (77F) across the southeast on Thursday with the mercury dropping slightly by the weekend while staying above normal for the time of year.
Mr West said: “This is such a big area of low pressure that it is actually drawing warm air up from the tropics and bringing it into the UK.
“We have got a sort of conveyor belt of warm air being pulled up from the Atlantic through the next couple of days.
“Towards mid-week a region of high pressure will build over France and western Germany putting Britain in a battleground between both pressure systems.”
Sunseekers are in for a week of blistering hot weather across Britain
He added: “The north and west will continue to experience some wet and windy weather while the south and east, which are closer to this high, will continue to enjoy high temperatures and dry conditions.
“The whole of the UK’s weather over the next few days will be coming up from the warm part of the Atlantic.
“We are seeing temperatures higher than average for the time of year, we expect to see around 25C (77F) on Thursday.”
While much of the country will hold on to the warm conditions through the weekend temperatures will fall off slightly, he said.
London Marathon runners should escape the worst of the blistering heat although thermometers could nudge 20C (68F) in the capital on Sunday, making conditions extremely difficult for athletes who have trained through a freezing British winter for the race.
Some weather maps show temperatures hitting 28C (82.4FF) in the southeast on Thursday with highs of between 23C (73.4F) and 25C (77F) likely across southern Britain.
Scotland and the north will be cooler although temperatures will hover between 15C (59F) and 20C (68F) through the coming days.
The London Marathon weather forecast is looking extremely hot for runners
Bookmaker Ladbrokes is offering 4-7 on the mercury hitting 25C (77F) anywhere in the country over the next week.
Spokeswoman Jessica Bridge said: “The sun’s shining and the thermometer’s rising which means the odds are falling.
“It looks like next week’s weather will be a scorcher and hopefully it’s the early signs of a long and hot summer.”
Exacta Weather forecaster James Madden said: “Many parts of the country can finally look forward to our first burst of summer for this year, with ample amounts of sunny spells and dry weather.
“Southern regions could also see maximum temperatures exceeding the mid to high 20Cs in the best of the sunshine, and there is a chance we could see or get close to the all time maximum daytime temperature for April.”
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