Tropical air could cause temperatures to soar past 30C in parts of the UK, making it hotter than California by the end of the week, after heavy rain lashes the country.
High pressure is set to build from the middle of next week, meaning southeast England could reach 32C on Friday, according to the Met Office – higher than the 26C predicted in Los Angeles.
However, it will come after most of the country is inundated by heavy and persistent rain from Sunday evening into Monday.
A weather warning could be imposed on parts of north Wales, with two inches of rain set to fall on Monday – about half a month’s worth for the area.
It comes after the UK experienced its sixth-wettest July on record, with flooding and strong gusts from Storm Antoni bringing a miserable start to August.
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Met Office forecaster Dan Stroud said: “We are looking at the possibility of reaching the low 30s later in the week, most likely on Friday, probably in and around London, running into East Anglia and other parts of the south and east.
“We’ve got low pressure dominating at the moment, that will eventually give way to another area of heavy rain and cloud which will move up from the south and west into Monday, which will be a miserable and wet day across England and Wales.
“Beyond that, there are tentative signs of an improvement, gradually losing that showery signal during Tuesday and Wednesday, and temperatures will start to climb.
“We’ve got high pressure building from the middle of the week and that will tap into some tropical continental air, which will draw up some very warm, locally hot air that will allow temperatures to climb steadily.
“By the time we get into Friday and maybe into Saturday we stand a chance of breaking into the 30s.”
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Much of England and Wales set to surpass 25C
Temperatures could also climb in other parts of the country on Friday, with much of England and Wales set to surpass 25C, while Scotland and Northern Ireland could reach the low-to-mid 20s.
Many areas will be dry with sunny spells during the warm period, according to the Met Office, though there may be outbreaks of thunder showers.
But Mr Stroud said the heat will be short-lived as low pressure will move back in, causing more unsettled conditions next weekend.