Severe weather warnings have been issued for Dundee, Tayside and Fife, with half a month of rain expected to hit the region today.
Flood alerts for Dundee and Angus are in place as the area prepares for three days of thunderstorms, high winds and torrential rain.
Forecasters say the weather could cause power cuts, travel chaos and lightning strikes across the country.
Flooding is possible across the whole of the weekend with a “yellow” weather warning in effect all day on Friday as a band of heavy rain pushes its way across Scotland.
The warning for thunderstorms and a “torrential” downpour will be in place between around 11.30pm on Saturday until 6am on Sunday.
The extreme weather has already caused organisers to cancel the Perth Highland Games this wekeend.
And the dire forecast is also bad news for those competing in the inaugural Women’s Tour of Scotland, which is set to begin in the city today.
The cycling tour, which has brought up to 20 of the world’s leading teams to the City of Discovery, is set to kick off at Slessor Gardens at 12.15pm today.
But those competing may wish to bring their swimming goggles as well as their lycra as they
battle the elements.
A Met Office forecaster said: “Rain is continuing through the afternoon on Friday with 30mm-40mm of rain possible – half a month’s worth of rainfall. It is a cloudy and wet day.”
The Scottish Environment Protection Agency (SEPA) has also issued a flood alert for the whole of Dundee and Angus.
It warns that homes, roads and low-lying land could be at risk from the rainfall and overflowing rivers.
“A band of heavy, persistent rain will push northward through Friday. This may lead to localised flooding from surface water and smaller rivers,” said the forecasting service.
“Built up areas and the transport network are at greater risk where possible impacts could include: flooding of low-lying land, roads, properties and disruption to travel throughout the day.
“Heavy and thundery showers are likely to develop in the area throughout Saturday although not all places within the alert area will see them.
“Where these do occur this may lead to further localised flooding from surface water and smaller rivers.
“Built-up areas and the transport network are at greater risk where possible impacts could include: flooding of low-lying land, roads, properties and disruption to travel.
“Remain vigilant and remember, it is your responsibility to take actions which help protect yourself and your property.”