Heavy rain has led to disruption to road, train and air travel across the south-east of England.
The Met Office has issued two yellow severe weather warnings for rain until 23:59 BST on Friday.
West Sussex, East Sussex, Kent and Surrey would be affected, officials said.
The Environment Agency has also issued a flood alert – meaning flooding is possible – for Scrase Bridge and West Common streams in Haywards Heath and Lindfield.
Met Office chief meteorologist Jason Kelly said the rain would be “persistent for some”.
“Rainfall totals of 15-30mm are expected widely, however the wettest areas are likely to see 40-60mm through the whole of Friday, with a lower likelihood of a few areas seeing as much as 75-100mm,” he said.
He said rain may be accompanied by thunderstorms across the South East during Friday afternoon and evening.
Commuters and motorists were also warned to expect spray and sudden flooding, leading to difficult driving conditions, road closures and other travel disruption.
A London Gatwick spokesman said temporary air traffic control restrictions were put in place due to the adverse weather.
“Some flights may be delayed,” he said. “London Gatwick apologises to passengers for any inconvenience.
“Passengers should contact their airline for further information.”
The Environment Agency said the Scrase Bridge and West Common Streams were “high and rising”.
“In the last 12 hours, 20mm of rain has been recorded at Haywards Heath,” a spokesman said.
“From 14:30, minor flooding could affect a small number of commercial properties on Bridge Road and residential properties on West Common Road.”
A tree on the railway line near Paddock Wood is also affecting train services between Ramsgate, Kent, and London Charring Cross.
Trains were also delayed between Farnham, Surrey, and Aldershot, Hampshire, due to flooding on the tracks. These services have since returned to normal.