The Met Office has issued weather warnings for London and the south east as heavy rainfall is set to strike.
As parts of the UK face up to a month's rainfall in the next two days, London and Surrey have been placed on 'amber warning' of severe weather.
A Met Office forecaster said: "The public should be prepared for the possibility of surface water flooding, particularly within the Amber area, where there is an increasing likelihood of river flooding, disruption to travel and outdoor activities.
"The rain across central England, East Anglia and southeast England should ease later in the day."
And the outlook for this evening and the weekend was also bleak, as more rain and thundery conditions look set to hit.
"Variable cloud with a few clear intervals [tonight] and just a little rain here and there but dry for the most part, although more persistent rain may reach Hampshire later," the forecaster said.
"[On Saturday], some bright or sunny intervals but also with heavy and thundery showers developing, especially by the afternoon."
Temperatures are set to reach 21C as the Wimbledon finals take place in SW19.