A high-level warning has been issued for the hot weather. The Level 3 heat-health alert covers London, the east of England and the South East of England.
It comes as parts of the UK could bake in temperatures of 34C (93.2F) on Friday. The Met Office said London and potentially some spots in East Anglia are most likely to reach the 34C high, making it the hottest day of the year so far.
Away from the capital and the South East, 27-30C is expected across most of England and Wales. Meanwhile, firefighters are warning that there is an increased risk of fires due to the heatwave.
The Level 3 Heat-Health alert for London, the East of England and the South East is in place to help protect health services, the UK Health Security Agency (UKHSA) has said.
Agostinho Sousa of the UKHSA told BBC Breakfast the alert is to help protect the NHS, adding: “The Level 3 alert is operational and called ‘heatwave action’. It is to inform our partners that they should prepare their services for possible increases in demand due to increases in temperatures.
“We also have a Level 2 that is currently active in the South West and East of England that is to inform our partners that they should prepare their services in case they need to enter into action in case we see an increase in temperatures.
“Right now the situation is stable, and we expect the temperatures to drop tomorrow.”