The Met Office has issued a thunderstorm warning for a wide area today (Tuesday 21 may) including Brighton and Hove.
Up to 2in or about 50mm of rain could fall and possibly some hail with road spray and flash flooding possible.
The official forecaster issued the warning for the rest of the day – until midnight – and said: “Heavy rain and thunderstorms may lead to some disruption.
“While some places may remain mostly dry, areas of heavy rain and some thunderstorms are expected to develop from around mid-morning.
“In the south of this warning area, the focus is likely to be slow-moving heavy showers and thunderstorms, perhaps with hail and lightning, which should gradually ease away later on Tuesday evening.
“Meanwhile, further north in the warning area, early showers are likely to merge into more general rain, this heavy and thundery at times, and will persist onwards into Wednesday – which is covered by a separate warning.
“Across the warning area, 20mm to 30mm in one hour or less is possible but perhaps most likely to the south of London, with a few places perhaps receiving 40mm to 50mm in two to three hours.”
The Met Office urged drivers to take care but also had advice for home owners and tenants.
It said: “Before gusty winds arrive, check to ensure moveable objects or temporary structures are well secured. Items include bins, garden furniture, trampolines, tents, gazebos, sheds and fences.”