Thunderstorms and heavy rain are forecast to lash England and Wales over the weekend, triggering warnings of flooding and travel disruption. The Met Office has issued a yellow thunderstorm warning for large swaths of England and Wales on both Saturday and Sunday. 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 mid-20s. 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.” However, areas in Scotland and north-west England and Northern Ireland are expected to stay dry with a few sunny spells, following a week of heavy rain. Box attributed this to winds, causing an “east-west” split in northern areas. The weather warnings for parts of England and Wales are likely to be in place going into Monday.