A national emergency has been declared for areas including London, Manchester and York.
Reports suggest millions of workers will stay at home over the next 48 hours to escape the heatwave’s peak.
The extreme warning means there is a risk to life and authorities are urging residents to make changes to their daily routines in order to stay safe.
Speed restrictions are likely to be imposed for trains, while some schools will close early and hospital appointments cancelled.
The National Health Service (NHS) is also concerned there will be greater demand for ambulances, warning patients could left outside hospitals in emergency vehicles.
Experts believe the extreme temperatures Europe is currently facing can be attributed to climate change.