Heavy rain is expected any time from this afternoon through to tomorrow morning (Sunday 18 February).
The Met Office issued a yellow weather warning covering a wide area including Brighton and Hove, with the prospect of at least half an inch falling within 18 hours and probably more.
The official forecaster said: “Rain may cause some travel disruption and flooding later Saturday through to Sunday morning.”
It could affect bus and train services, with journey times taking longer, and drivers were warned to beware of spray and flooding on roads.
The Met Office also said: “Flooding of a few homes and businesses is likely.”
And it warned people that power supplies and other services could face interruptions.
The forecaster added: “Rain will move east across England and Wales during Saturday afternoon and night before clearing south east England on Sunday morning.
“With this rain falling on already saturated ground, impacts are more likely.
“Many places are likely to see 10mm to 15mm of rain, although 30mm to 40mm is possible over higher ground in western areas.
“There is a small chance that rain hesitates as it clears east on Sunday morning which may allow these higher accumulations to fall in a few places across central, southern and eastern England.”
The Met Office urged those living in flood-prone homes to “check if your property could be at risk of flooding”.
It said: “If so, consider preparing a flood plan and an emergency flood kit.
“Give yourself the best chance of avoiding delays by checking road conditions if driving – or bus and train timetables – amending your travel plans if necessary.
“People cope better with power cuts when they have prepared for them in advance. It’s easy to do. Consider gathering torches and batteries, a mobile phone power pack and other essential items.
“Be prepared for weather warnings to change quickly. When a weather warning is issued, the Met Office recommends staying up to date with the weather forecast in your area.”
