The Met Office has warned of “sudden flooding” and more thunderstorms in Dundee, Angus, Fife and parts of Perthshire.
The forecaster has issued a yellow warning for thunderstorms across most of Courier Country, valid from 3pm Thursday until 4am Friday.
The warning says that potentially record-breaking temperatures on Thursday could sparking scattered thunderstorms later in the day, continuing overnight.
It adds: “Spray and sudden flooding could lead to difficult driving conditions and some road closures.
“Where flooding or lightning strikes occur, there is a chance of delays and some cancellations to train and bus services.
“There is a chance that power cuts could occur and other services to some homes and businesses could be lost.
“There is a small chance that homes and businesses could be flooded, or damaged by lightning strikes, hail or sudden gusts of wind.”
The fresh warning comes after lightning caused havoc across Courier Country early this morning.
Rail services between Perth and Inverness are cancelled this morning due to a lightning strike on the train line.
In Fife, occupants of a house in Markinch escaped injury after a lightning strike sparked a fire.
The heatwave is expected to peak on Thursday with temperatures of up to 30C expected in parts of Scotland – hotter than the likes of Barbados, which is due to be 28C on the same day, and Lisbon, Portugal, at 27C.
Locally the hottest place is expected to be Perthshire where the mercury could climb to 27C.
The Met Office says there is a chance that Scotland’s 2019 high of 30C, set on June 28, may be broken on Thursday.
There is also a chance that the UK’s all time record of 38.5C could be bested south of the border come Thursday.
Temperatures in Scotland hit a high of 28.1C in Scotland on Tuesday with the hottest local spots being Leuchars at 24.8C and Strathallan Airfield at 24.6C. The UK’s hottest place was Northolt, London, at 33.7C.