Thunderstorms are set to cause flooding and travel disruption across parts of England, according to the Met Office.
The forecaster has issued an amber thunderstorm warning for the east and south east of the country.
Storms in northern France are expected to move across the Channel to strike the East, London and the Home Counties.
Between 3cm and 4cm of rain is set to fall within two hours after 17:00 BST, which could lead to flash flooding.
“Flooding of homes and businesses is likely and could happen quickly, with damage to some buildings from floodwater, lightning strikes, hail or strong winds,” the Met Office said.
The forecaster says there is a risk of power cuts, flooding and travel disruption, while fast-flowing water could pose a “danger to life” in some cases.
Lightning, hail and gusty winds are also expected.
People are being warned of potential travel delays, road and rail closures and power outages.
A yellow weather warning for rain is also in place covering central and southern parts of the country.