Forecasters have told locals across Tayside and Fife to brace for thunderstorms.
A Met Office yellow warning will be in effect in the area, and neighbouring Grampian, from 2am until 2pm on Saturday.
The forecaster said thunder and lightning, “torrential rain”, “large hail” and flooding could occur as the stormy conditions spread into the north-east.
Up to 1in of rain could land in the space of an hour as the poor weather moves into the area.
The Met Office said buildings and other structures could be at risk from lightning strikes, while driving conditions could be affected by the downpour or hail. Power cuts could also take place.
A Met Office statement said: “Thunderstorms will become more widespread across north-east Scotland during the early hours of Saturday morning, perhaps merging into longer periods of heavy and thundery rain.
“Where the thunderstorms occur, torrential downpours are possible with 20 mm of rainfall in 1 hour and perhaps 30-40 mm in 2 or 3 hours.
“Large hail, frequent lightning and strong and gusty winds will be additional hazards. The thunderstorms will become less frequent and the risk of disruption will decrease on Saturday afternoon.”
Thunderstorms are forecast in England overnight from Friday into Saturday.