Heatwave: How to stay safe in high temperatures
19 July 2013 Last updated at 14:25 BST
The north-west of England has become the latest area to be issued with a level three heatwave warning.
Healthcare services are being advised to help vulnerable people, such as the elderly and young children.
South-west England and the West Midlands remain on the same level of alert, but the warning has been lowered in London and south-east England.
Jessica Harris, from Cancer Research, said people should take extra precautions when spending time in the sun.