A yellow “be aware” weather warning is in place across all of Wales and Northern Ireland, and most of England and Scotland, as some places could receive more than two inches of rain.
Ms Kent added: “The first band of rain could bring 30mm of rain in places, and if you draw the short straw, then you could get another 30mm with the showers that follow.
“Some places might get as much as 60mm of rain.”
A yellow weather warning for wind across all of Wales and central and southern England follows on Saturday.
Although Scotland and northern England escapes the wind warning, a yellow guidance is in place for thunderstorms.
Ms Kent said “it will be unseasonably windy”, with gusts in the warning area reaching 40 or 50mph.
In more exposed areas, the winds could be even higher.
Ms Kent added: “The English Channel coast could see winds in excess of 60mph.
“Saturday is going to be a very unseasonal day, it could feel more like autumn than August.”
Due to the forecast, people travelling over the weekend are being warned to expect delays and disruption to their journeys.
Boardmasters music festival in Newquay, Cornwall, was cancelled at the 11th hour in anticipation of the bad weather.
While performances at the event, which included slots from stars such as Wu-Tang Clan, Florence + The Machine and Foals, were not due to begin until Friday, doors were set to open to visitors on Wednesday.
In a statement posted on Twitter at 11pm on Tuesday, the festival said “we sincerely regret the disappointment to fans, and apologise for any disruption caused to local businesses”.
It added: “The safety of you, the fans and attendees, as well as performers and crew comes first.”