The Met Office has issued its first-ever red warning for extreme heat, as it warned of a "potentially very serious situation".
Temperatures across the UK could reach 40C meaning a risk to life is likely. Merseyside, which has been included in the red warning, will see highs of 36C.
The red warning is in place from Monday at 12am to Tuesday at 11.59pm. The Met Office said: "Exceptional, perhaps record-breaking, temperatures are likely on Monday, then again on Tuesday.
READ MORE: Lifeguard issues warning to anyone going to the beach during the UK heatwave
"Nights are also likely to be exceptionally warm for the UK, especially in urban areas. This is likely to lead to widespread impacts on people and infrastructure."
Grahame Madge, Met Office spokesman, added: "We've just issued a red warning for extreme heat for Monday and Tuesday which is the first such warning ever issued. This is potentially a very serious situation."
It is expected there will be population-wide adverse health effects experienced, not limited to those most vulnerable to extreme heat, leading to serious illness or danger to life. Government advice is that 999 services should be used in emergencies only; seek advice from 111 if you need non-emergency health advice.
Substantial changes in working practices and daily routines will be required as there is a high risk of failure of heat-sensitive systems and equipment, potentially leading to localised loss of power and other essential services, such as water or mobile phone services.
Significantly more people visiting coastal areas, lakes and rivers, leading to an increased risk of water safety incidents.
And delays on roads and road closures are also expected, along with delays and cancellations to rail and air travel, with significant welfare issues for those who experience even moderate delays
Temperatures are expected to drop away from Wednesday onwards.
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