The Met Office has triggered a 'level three' amber alert for hot weather in parts of England over the next few days, with temperatures expected to soar to 30°C on Saturday.
The alert activates the national heatwave plan, which calls on GPs, district nurses and social workers actively to identify and protect vulnerable patients on their practice lists.
NHS England area teams will contact GPs directly with updates on the heatwave alerts.
A 'level two' alert is in place for the East of England, south-east England, London and the south-west. These are triggered when the Met Office forecasts a 60% chance of heatwave conditions for two days or more.
A 'level three' alert has also been announced for the East Midlands and Yorkshire and the Humber regions. This occurs when forecasters predict a 90% chance of a heatwave. It automatically activates the NHS heatwave plan, which requires health and social care services to target high-risk groups.
Health officials urged people to keep out of the sun between 11am and 3pm, wear sunscreen and drink plenty of water.
Health and social care workers should 'regularly check on vulnerable patients, share sun safety messages, make sure room temperatures are set below 26°C and ensure patients have access to cold water and ice', they said.
Dr Angie Bone, heatwave plan lead for PHE, said: 'While many people enjoy hot weather, high temperatures can be dangerous, especially for people who may be particularly vulnerable such as older people, young children and those with serious illnesses.'