Thunderstorms and heavy rain may cause travel disruption across parts of southern England and Wales, the Met Office has warned.
The weather service has issued a yellow thunderstorm warning from 4pm to 11.59pm on Monday across much of South Wales, South West England, and parts of southern England.
The Met Office said there was a “good chance” that driving conditions will be affected by spray, standing water or hail, adding that delays to train services are possible.
Frank Saunders, a chief meteorologist at the Met Office, said: “Areas of heavy showers and thunderstorms will move northwards across southern parts of England and Wales later this afternoon before clearing northwards overnight.
“It’s possible that some places could see 20-30mm of rain within two to three hours, with a small chance that a few places could receive 40mm.
“Thunderstorms are most likely for south-facing coastal districts, and hail and some strong gusts of wind could accompany the heaviest showers and thunderstorms.”
Further heavy showers and thunderstorms are expected across central and southern areas of the UK on Tuesday.
A longer period of heavy rain is also expected over parts of south-east Scotland and north-east England later on Tuesday through to Wednesday.
The weather service said it also had “increasing confidence” that ex-Hurricane Kirk will track to the south of the UK, bringing heavy rains and strong winds to northern France.
Although north and south shifts remain possible, the threat of significant impacts to the UK from the ex-hurricane are now much reduced, it added.
The Met Office said temperatures would decrease from Wednesday in the north, with all areas experiencing below average temperatures from Thursday.
Night frosts are also expected for some regions later in the week, and snow is possible for the higher mountains of Scotland.