Severe weather warnings and flood alerts are in place across the country as another day of rain is expected.
Heavy showers will cover large swathes of the UK for another two days as an area of low pressure continues to move slowly across the country, the Press Association reported.
Wales, the North West, Yorkshire and Humber, the West Midlands, the East Midlands, the east of England, the South West and South East could all see as much as 25mm of rain in an hour.
The Met Office has put yellow warnings in place and advised that localised flooding and travel disruption are likely in the areas affected by heavy rain.
The warnings are also in place for Thursday when lightning is an additional hazard.
The chief forecaster said: "Rising temperatures will trigger slow-moving heavy showers and thunderstorms.
"Once again, 15mm-25mm are likely to fall within an hour in scattered locations, bringing the risk of flooding, especially across urban areas."
The Environment Agency has issued 21 flood alerts indicating that flooding is possible, and warned people to be prepared.
The alerts cover areas in Cheshire, Merseyside, Derbyshire, Nottinghamshire, Northamptonshire, Oxfordshire, Buckinghamshire, the West Midlands, Staffordshire, Norfolk, Lincolnshire and north-west and north-east Greater London.
Last weekend saw flash floods hit south London for the second time that week causing delays and closures in Purley.
Last Tuesday, heavy down pours led to three cars becoming completely submerged under a bridge on Wallington High St, with the downpour causing depths of up to two metres in just minutes.