The Met Office has issued warnings for rain and thunderstorms – with the alerts in place until Thursday morning.
The first began at 8pm and covers an area stretching from Portsmouth to Plymouth, and northwards to South Wales, and lasts until 8am on Thursday.
Heavy rain is expected, with a chance of thunderstorms, and the Met Office said it could bring difficult driving conditions and some flooding.
The second warning kicked in at 11pm and covers nearly all of southeast England, stretching as far north as Oxford and including London. It’s in force until 6am on Thursday.
“Thunderstorms are likely at times later this evening and overnight, leading to travel disruption and some flooding,” said the Met Office.
There’s also a chance of hail and strong winds.
Around 2cm to 4cm of rain is expected overnight, with 5cm possible in some places.
“Much of this rain may fall over a two or three-hour period,” the Met Office said.
Met Office meteorologist Alex Deakin said: “You may well get woken up tonight by a rumble of thunder, or some flashes of lightning across parts of the South.
“A lot of heavy rain falling in a short space of time as well.”
He said it could create a lot of spray and surface water on the roads for commuters on Thursday morning.
Conditions remain otherwise dry, with temperatures near double digits in England and Wales and around 8°C to 9°C in cities further north.
Mr Deakin said: “It was rather cloudy at the beginning of Thursday, but there was still heavy rain in the south-west early in the morning.”
“This should be an improving trend, but in the south… There is always a chance of further rain.” Parts of England, central and southern Wales.
He added: “Most of north-west Scotland, Northern Ireland, north-west England and the Midlands as far as East Anglia should be clear tomorrow.”