An amber weather warning is in force with thunderstorms threatening to bring torrential rain across the county today.
The warning was issued by the Met Office for the south east and London and other parts of the country from 4am to 11am.
Forecasters say there will be torrential rain, with thunderstorms in places, which could lead to some significant surface water on roads this morning.
The Met Office warned that between 20mm and 40mm of rain could fall within an hour in the amber zone, rising to between 70mm and 100mm in just a few hours, in places where downpours persist.
Storms could cause flooding in some areas and pose a risk of danger buildings which could be damaged by floodwater, lightning strikes, hail or strong winds.
The warning says heavy rain could create “fast flowing or deep floodwater, in some areas causing a danger to life”.
A spokesman said: “Torrential rain, with thunderstorms in places, could lead to some significant surface water flooding during Saturday morning.”
More urban areas could be hit with “significant impacts” and in places, homes or businesses could flood, with the flooding happening quickly in some communities, which could be cut off if roads flood.
The affected area is also covered by a yellow warning for thunderstorms, which came into place for the north of England, Midlands and eastern half of the country from midnight and runs until 9pm today.
Frequent lightning and localised surface water flooding are also possible.
Chief Met Office meteorologist Andy Page added: “Intense rainfall will impact parts of the UK as thunderstorms move in from France.
“This weekend is expected to be busy on the roads as more schools in England and Wales break up for the summer holidays, so it’s important people keep up to date with the very latest forecast.”
