Train journeys are being affected as Norfolk is set to experience some "pretty lively showers" throughout Sunday evening.
Passengers travelling from Norwich to London Liverpool Street have been impacted, due to heavy flooding on the railway, with some services cancelled.
Met Office meteorologist Steven Keates said parts of the south between south Suffolk and the Isle of Wight could be deluged by 100mm of rain in just a few hours on Sunday evening.
He said: "There's torrential thunderstorms around yet again.
"Into the evening, from Norfolk to Bournemouth we are going to see some pretty lively showers.
"Torrential downpours, thunder and lightning and potentially some hailstones are settling in the south."
The Met Office issued a yellow weather warning for heavy rain and thunderstorms, covering parts of Norfolk.
This means spray and sudden flooding which could lead to difficult driving conditions and some road closures and power cuts might occur to some homes and businesses.
Officers in Norfolk Fire and Rescue Service control room are assisting colleagues in London, which has seen flash flooding in parts during Sunday afternoon.
Norfolk and Suffolk Roads and Armed Policing Team have tweeted that Ehringhausen Way, Haverhill, is being affected by severe flooding and motorists are urged to find alternative routes.
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