Pedestrians walking around London - where most of the flash flooding is expected - were seen running for cover and cowering under raincoats and umbrellas when the torrential rain struck suddenly.
Meanwhile, firefighters in Willenhall, West Midlands rescued a 76 year old man and 2 dogs from floodwater as whole streets filled up and cars were abandoned in Birmingham.
Thirteen houses have been flooded and a commercial premise was evacuated by specialist boat teams of firefighters after flash flooding on Middlemore Road in Smethwick, Birmingham
The Met Office said that in some places, up to 30mm could fall in an hour - only slightly less than the 35mm seen yesterday - which puts Britain, and particularly London, at risk from more flash flooding.