It will be a fresher day with temperatures expected to reach around 18C (64F) in Glasgow and 22C (71.6F) in London.
Met Office forecaster Emma Boorman said: “There could be the odd rumble of thunder away from the South East as those showers bubble up, but there should be some sunny spells outside them.”
South Farnborough saw 54.6mm of rain fall on Thursday, around the monthly average for June, as torrential rain swept in from the Channel causing widespread travel chaos.
Abellio Greater Anglia and Network Rail apologised for the disruption to services between Norfolk, Suffolk, Essex and London on Thursday but said a full service is expected to run on Friday.
“This is due to extensive flooding, caused by heavy rain, affecting both the tracks and signalling equipment, which has necessitated the closure of the lines between Ilford and Stratford,” a statement said.
Thameslink said trains would be running on Friday but explained there may be some cancellations.
South West Trains said disruption is due to continue until midday on Friday with queuing systems in place if there is overcrowding at stations.
Southern Railway said it was hoping to run its service as normal but advised to check before travel.