The Met Office has warned that thunderstorms, hail and heavy rain could bring flash flooding to large parts of drought-hit Britain this week, with some areas potentially seeing a month's worth of rain within a matter of hours. The warning comes as the UK nears the end of an exceptionally hot and dry summer that has left nearly three-quarters of England and all of Wales in drought, with 28 million people currently under hosepipe bans.

Forecasters say dry, sunny conditions will hold through the start of the week before turning unsettled from Wednesday, as warm, humid air brings widespread showers and thunderstorms, particularly to England and Wales. Local rainfall totals of up to 30mm could fall within three to four hours, with cumulative totals reaching as much as 60mm, potentially exceeding the combined rainfall of the past two months in the worst-hit south-east. Rivers and reservoirs remain critically low after record dry spells, including 62 consecutive dry days in Surrey, and seven English reservoirs are now classed as having "exceptionally low" storage, prompting concern that rain falling on hardened ground could trigger localised flooding.