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.
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Elsewhere, it will stay dry with temperatures mostly holding up in double figures across England and Wales, or staying at around 8C to 9C in towns and cities further north.
Deakin said: “A cloudy start then to Thursday one way or another, still some heavy bursts of rain early on across the South West.
“That should tend to clear away, but always the likelihood of further showers across southern parts of England, Mid and South Wales.”
He added: “Parts of northwest Scotland, Northern Ireland, northwest England, much of the Midlands down towards East Anglia should have a fine and sunny day tomorrow.”