Thunderstorms and heavy rain are forecast to lash the UK over the weekend, including Merseyside, triggering warnings of flooding and travel disruption.
The Met Office has issued a yellow thunderstorm warning for large swathes of England and Wales on both Saturday and Sunday.
They will also continue into Monday.
Flooding could cause roads to close, while extreme weather may damage buildings and cause power cuts and cancellations to train and bus services.
Forecasters also expect the weekend to be much cooler, following a week of hot and humid weather, with top temperatures reaching the early twenties.
The south of England and Wales are likely to be the wettest areas, with frequent lightning, gusty winds and heavy downpours with 30 to 40mm of rain possible in less than an hour, according to the Met Office.
Five flood alert warnings have been issued across the West Midlands by the Environment Agency.
Matthew Box, a Met Office forecaster, said: "Saturday will begin mostly cloudy for most areas across the UK but as the day goes on showers will start to break out in the south and south east of England.
"As the day progresses further there's a chance of some rumbles of thunder and potentially some hail and lightning.
"The risk of thunder will start to push further north on Sunday, with central parts of England and Wales facing heavy rain and the chance of flooding."
The weather warnings for parts of England and Wales are likely to be in place going into Monday.
Saturday's forecast for the Meteogroup said: "Scattered showers across central and southern England and Wales this evening and will track north-westwards overnight to reach Northern Ireland and northern England by dawn.
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"Showers will be locally heavy and persistent with thunder at times.
"Further showers will also edge into south-west England."