Environment Canada has issued a severe thunderstorm warning for the Halifax area.
"Take cover if threatening weather approaches," it warned.
The storm path includes Elmsdale and Waverley and is moving eastward.
Environment Canada has also issued thunderstorm watches for Antigonish, Colchester, Cumberland, Guysborough, Hants and Pictou counties.
Large hail is also falling, prompting the agency to warn that it can cause property damage and injure people.
The impending storm also delayed the annual Natal Day Regatta on Lake Banook. The race included Olympic medal winner Mark de Jong.
Participants are off the water for at least 30 minutes, until the sky is free of thunder and lightning.