Heavy rain and thunderstorms are expected from late tomorrow night (Monday 24 June), according to the Met Office.
The official forecaster has issued a severe weather warning for thunderstorms for much of the country for a 48-hour period.
Local forecasts suggest rain overnight tomorrow night and in the early hours of Tuesday (25 June).
And Wednesday, when thunder and lightning could still be in the air, wind speeds are expected to pick up.
As the cloud clears overnight on Wednesday and Thursday, the wind could gust at speeds approaching 40mph.
The Met Office warning said: “Heavy rain and thunderstorms may lead to flooding and disruption to travel.
“There is a small chance that homes and businesses could be flooded quickly, with damage to some buildings from floodwater, lightning strikes, hail or strong winds.
“There is a small chance of fast flowing or deep floodwater causing danger to life.
“Where flooding or lightning strikes occur, there is a chance of delays and some cancellations to train and bus services.
“Spray and sudden flooding could lead to difficult driving conditions and some road closures.
“There is a slight chance that power cuts could occur and other services to some homes and businesses could be lost.”
Later in the week the temperatures could rise again, approaching 75F or 23C.