A yellow heat health alert has been issued for the region by the UK Health Security Agency, with temperatures expected to climb close to 30 degrees Celsius for several days.
Health officials say the heat could have a serious impact on vulnerable Londoners, including older adults, people with existing health conditions, and those living in poorly ventilated homes.
The warm weather begins on Monday, with a clear and sunny day expected across the capital.
The temperature is forecast to reach a high of 29 degrees Celsius, with an overnight low of 19. Sunrise is at 5.40am and sunset at 8.30pm. UV levels will be high.
Tuesday will bring sunny intervals and continued heat. Temperatures are again forecast to peak at 29 degrees Celsius, with a nighttime low of 19.
By Wednesday, the heat will intensify slightly. The Met Office is forecasting sunny intervals and a maximum temperature of 30 degrees Celsius, with overnight temperatures again falling no lower than 19.
With little cooling overnight and consistently high daytime temperatures, health authorities are urging Londoners to take extra care.
Those most at risk include older people, young children, and anyone with chronic health issues.
People are being advised to keep their homes cool, stay hydrated, and avoid the sun during the hottest parts of the day.
Care settings and community health providers are also being urged to take action to support those most vulnerable during the heatwave.
