Large parts of Scotland are expected to be hit by thunder and lightning strikes.
Forecasters say lightning has been forecast in western and central areas on Saturday afternoon, and it could move into the east in the evening.
The Met Office also warned that thunderstorms could affect parts of south-east Scotland later.
It comes a day after a temperature of 30C (86F) was recorded in the Highlands.
But in southern England temperatures soared to 33.6C (92F), making it the hottest day of the year so far.
The Met Office said would be a “surge in frequent lightning activity” until Saturday evening.
It could lead to a short term loss of power or other utility services, and there could be damage to some buildings.
The Met Office added: “Although heavy rain is possible, perhaps with locally 10-15mm inside an hour later today, lightning strikes seem the more likely hazard.
The warning of thunderstorms in the south-east of Scotland is in place until about midnight.
Forecasters said it could lead to sudden flooding and spray, causing difficult driving conditions.