The Met Office has forecast temperatures potentially reaching 40C on Monday and Tuesday (18-19 July), with exceptional heat expected across much of England. 40C would be a new record high for the UK.

The warning says that the high temperatures could lead to “serious illness or danger to life”, as well as delays and cancellations to train and air travel. There could also be “significant welfare issues for those who experience even moderate delays”.

Network Rail said that people should only travel on Monday “if absolutely necessary” with speed restrictions being introduced on railway lines. There is also a “high likelihood of cancellations, delays and last-minute alterations”.

Met Office chief meteorologist Paul Gundersen said “Exceptional, perhaps record-breaking temperatures are likely early next week, quite widely across the red warning area on Monday, and focused a little more east and north on Tuesday. 

“Currently there is a 50% chance we could see temperatures top 40C and 80% we will see a new maximum temperature reached.”

While it is the first time that the Met Office has issued a red heat warning, this system was only introduced last year.