Rail passengers told to travel only if essential amid red extreme heat warning

Extreme temperatures in a heatwave can cause rails to expand and buckle, requiring lower speeds for safety. Photograph: Gareth Fuller/PA

Rail passengers have been told to attempt to travel only if “absolutely essential” and check trains are running, with extreme heat expected to disrupt services around Britain.

Temperatures are forecast to rise to 37C across most of southern England and Wales over the next three days, and potentially to 40C in the most affected areas.