A yellow weather warning has been issued covering the whole of the South West following the heatwave.
The Met Office says thunderstorms are set to develop in the region on Monday (15 August), bringing heavy rain and possible disruption.
It comes as an amber weather warning for extreme heat is currently in place for the region - with the possibility of an official drought being declared today (12 August).
In its warning, which runs from 6am to 11.59pm on Monday, the Met Office says there is a 'small chance' homes and businesses could be flooded quickly.
There is also the potential for lightning strikes, hail and strong winds.
"Where flooding or lightning strikes occur, there is a chance of delays and some cancellations to train and bus services," the Met Office said.
"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."