Referring to the regions covered by the warning Mr Miall said: “This area will widely see 10-15 millimetres of rain falling, probably within a space of 3-6 hours.
“For some areas we could see as much as 30-50 millimetres of rain, particularly south-east England where we will see some of the heaviest of that rain so there will be some tricky travelling conditions, some pretty nasty conditions on those roads with a lot of surface water and the risk of some flooding as well.
“Through Wednesday morning though we’ll see the worst of that rain coming in across the south coast and south-east England.
“There will be rain spreading further north and west as well, a little bit of uncertainty as to the boundary of that so do keep abreast of the latest forecasts.”
Source : https://www.express.co.uk/news/weather/1350272/UK-weather-forecast-Met-Office-warning-heavy-torrential-rain-Britain-wind-travel-ont