Motorists could face potential traffic chaos in parts of the country where forecasters say heavy storms may lead to flash floods.
Residents in parts of London, the South East and eastern England are being warned rainfall of up to 40mm over just a few hours could result in localised flooding in some areas.
After a heatwave on Monday that saw temperatures rise to the highest levels for the year, the country is now bracing for a spell of thunderstorms, rains and hail storms.
In Lewisham, Bromley, Greenwich and Croydon - London boroughs predicted to receive up to 30mm of rain - the Environment Agency has put out a flood alert for rivers.
But rivers in parts of east and central England - areas which have been declared to be in a state of drought following the dry spring weather - remain at low levels and face low risk of flooding, said a Met Office spokesman.
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