A top-level warning has been issued for the hot weather. The Stage 3 heat alert covers London, East England and South East England.
It comes as parts of the UK could bake in temperatures of 34C (93.2F) on Friday. The Met Office said London and possibly some places in East Anglia will most likely hit the 34C high, making it the hottest day of the year so far.
Away from the capital and the South East, 27-30°C is expected across most of England and Wales. Meanwhile, the fire brigade warns of an increased risk of fire due to the heat wave.
The Level 3 heat health alert for London, East of England and South East is intended to help protect health services, the UK Health Security Agency (UKHSA) has said.
UKHSA’s Agostinho Sousa told BBC Breakfast the alert was intended to help protect the NHS, adding: “The Level 3 alert is operational and is called ‘Heatwave Action’. It is intended to inform our partners that they should prepare their services for possible increases in demand due to temperature increases.
“We also have a Level 2 which is currently active in the south west and east of England which is intended to inform our partners that they should prepare their services should they need to take action should we see a rise in temperature.
“At the moment the situation is stable and we expect temperatures to drop tomorrow.”