A flood alert has been issued for Fife and parts of Tayside.
Sepa has issued a ‘be prepared’ flood alert for a large area north-west of Dundee, including Longforgan, Perth, Coupar Angus, Blairgowrie and Alyth.
The whole of Fife is subject to a flood warning.
A Sepa statement said: “Heavy thundery downpours are likely to affect areas across Scotland during Friday and again on Saturday.
“It is currently not possible to define exactly what areas will be affected and some areas will miss the worst of the heavy showers and thunderstorms.
“However, where these thunderstorms do occur they are likely to bring torrential rain. People should be aware and prepared to act.
“If these showers coincide with built-up areas there is a risk of surface water flooding to properties and roads, and disruption to infrastructure and travel.
“There is also a risk of flooding to properties and roads from smaller rivers and watercourses if the heavy downpours occur over small urban or fast responding catchments.
“Remain vigilant and remember, it is your responsibility to take actions which help protect yourself and your property.”
Dundee, Tayside and Fife are currently subject to a Met Office yellow weather warning for rain until 10pm today.
A separate yellow warning for rain has been placed on Perthshire and other parts of Scotland for Saturday between 11am and 9pm.
The statement regarding Friday added: “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.”