This afternoon (July 12) brings an official weather warning of flooding and travel disruption in Sussex, caused by heavy rain.
Met Office forecasters say slow-moving, heavy showers are likely, with thunderstorms in places.
If the most severe predictions come true, up to 90 millimetres of rain might fall in some places today.
A Met Office spokesperson said:
"Slow-moving, heavy showers, with some thunderstorms, are likely to break out during Monday afternoon.
"This may lead to torrential downpours in some places with 20 to 30 mm of rain in an hour and perhaps in excess of 60 mm in some spots in two or three hours.
"There is also a chance of more persistent heavy rain developing over parts of south east England during the afternoon or evening and persisting into early Tuesday.
"Were this to occur, there is a chance of 60 to 90 mm rain falling in a few spots."