The Met Office says gusts of up to 60mph and heavy rain are set to batter the UK on Wednesday.
They have issued a yellow weather warnings for wind and thunderstorms covering large parts of central England and Wales.
As a deep area of low pressure moves across the country, the strongest winds will be further to the south over northern France and the Channel Islands.
A yellow warning for wind is in place for southern parts of England from 4am to 6pm on Wednesday, while a yellow thunderstorm warning is in place between 9am and 7pm for parts of England and Wales.
Slow-moving thunderstorms could lead to rainfall accumulations of 20-25mm within an hour, while some locations could even experience 40mm in a two to three-hour period.
Met Office chief meteorologist, Dan Suri, said: “An unseasonably deep area of low pressure for the time of year will move into Ireland during the early hours of Wednesday then continue across Wales and England during Wednesday daytime.
“Heavy rain associated with this low will affect large parts of the UK tonight and on Wednesday.
“This deep low will also bring high winds into the UK on Wednesday, especially the south. Along the south coast the highest gusts will be during Wednesday daytime.”
Ellie Wilson, a meteorologist at the Met Office, said: “It’s unseasonably windy for the start of August but thunderstorms are not unusual at this time of year.
“Thunderstorms bring with them the associated dangers of lightning and hail.”
The bad weather could make for challenging driving conditions as holidaymakers travel across the UK.
Rod Dennis, a spokesperson for RAC said: “Drivers attempting to drive through patches of standing water risk losing control, so the best course of action is to slow down and carefully avoid them whenever possible.
“As the wind will be especially strong along southern coasts, drivers towing caravans will need to be cautious while those carrying items on the roof should make sure these are properly secured.”
The best chance of more widely settled weather will come in the second half of August, but the risk of thundery showers will remain, the Met Office said.
A period of prolonged or excessive heat is unlikely, with the chance of heatwaves being lower than some recent Augusts.