According to the weather experts, Wednesday will see a breakdown of the heat, with potential for thunder, especially in the southern half of England, and it will be wet for a time over much of Scotland and northern England. This comes as the rise in the mercury levels has led to Transport for London (TfL) advising passengers to only travel for “essential journeys”.
The Met Office forecast after the heat peaks reads: “Scattered showers remain likely to develop in places.
“Diurnal showers and perhaps longer spells of rain may also be seen over the weekend.”
For Monday and Tuesday rail passengers in England and Wales have been warned they should only travel if necessary, and Network Rail said speed restrictions were likely.
The TFL tweeted: “Only travel if essential due to very high temperatures being forecast.”
Some schools will also close early next week and some hospital appointments will be cancelled.
The rest of England, Wales and southern Scotland will be under an amber warning for extreme heat – while in Europe, deadly wildfires have broken out in Portugal, Spain and southwestern France.
A national emergency is declared when a heatwave is so severe and, or prolonged that its impacts extend beyond the health sector, according to the UK Health Security Agency (UKHSA).
Transport, food and businesses could also be affected and it could cause power or water shortages, according to the agency whose job it is to protect the population from health threats.
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Mr Barclay said: “The clear message to the public is to take sensible steps in terms of water, shade and cover. That’s the best way of mitigating against the heat.
“We’re asking people to keep an eye out for their neighbours and those who may be vulnerable.”
The Met Office described the forecast heat that is coming from France and Spain as “absolutely unprecedented” and urged people to treat it like a storm warning and consider changing plans.