The Met Office has issued a weather warning with thunder, lightning and heavy rain forecast overnight and into tomorrow morning (Monday 18 September).
It could mark the start of a stormy week as the tail end of Hurricane Lee makes its way across the Atlantic.
While the storm will be much less powerful, it is expected to bring an end to the recent warm dry weather.
The official forecaster said: “Heavy showers and thunderstorms are likely to arrive across southern England during Sunday and move northeastwards through the afternoon.
“From late afternoon through Sunday night there is a small chance of thunderstorms becoming severe, with large hail, frequent lightning, gusty winds and torrential rain producing 30mm to 40mm in an hour.
“The most likely scenario is that impacts are more limited and isolated but should these more severe storms develop, flooding and disruption could occur.”
When the Met Office issued the yellow thunderstorm warning, it said that there was “a small chance of disruption from severe thunderstorms later on Sunday”.
The forecaster said: “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.
“Where flooding or lightning strikes occur, there is a chance of delays and some cancellations to train and bus services.
“There is a slight chance that power cuts could occur and other services to some homes and businesses could be lost.
“Spray and sudden flooding could lead to difficult driving conditions and some road closures.
“There is a small chance of fast flowing or deep floodwater causing danger to life.”
Some forecasts suggested that a month of rain could fall by the morning.