The Met Office has issued a yellow weather warning across huge swathes of the country with heavy rain and thunderstorms expected to batter Britain.
Short but severe showers will move from the south-west in the morning to the north-east by the evening.
Meteorologists have warned flooding could hit businesses and homes in areas hit by the worst downpours.
Commuters in London can also expect a sodden commute into work in the morning, while workers in the north will be battered with rain as they head home.
Police forces around the country have put out warnings urging people not to travel unless necessary in the bad weather.
Quite a change in the weather this week…
Here are the details: 🌧️🍂🌬️ pic.twitter.com/grF1xcqYUF
— Met Office (@metoffice) September 23, 2019
Craig Snell, a meteorologist at the Met Office, told the Standard: “We are expecting some fairly heavy rainfall, with 15 to 30 millimetres in most areas.
“In some places we could see around 70mm.
“We could see a month’s worth of rain in a few locations in a few hours.”
Mr Snell went on: “Tomorrow morning we’ll start to see a band of heavy rain move across the West Country.
“It will move up the country and be over London during the morning rush hour.
“During the day the band will work its way northwards, and by the evening rush hour will be over areas of the north east such as Newcastle.
“In the south, commuters can expect difficulty getting to work, and in the north, difficulty commuting home.
“But by this stage southern parts of the country should be a bit drier.
“The heavy rain could lead to problems if it’s over a town.”