The storm hit the island of Montreal at around 3 p.m., as black clouds suddenly covered the sky.
Rain and wind gusts as strong as 90 km/h knocked down trees and caused flooding in some areas.
Dozens of flights at Trudeau airport were delayed by the winds.
City of Montreal officials said traffic lights on some streets around the city were out of order and urged drivers to reduce speed.
Hydro-Québec said that at around 5 p.m. there were almost 30,000 homes and business without power — most of them in Laval, Montreal and the Montérégie.
One place hard hit by the storm was McGill University, where a convocation ceremony was underway.
Outdoor tents where the ceremony was taking place were evacuated as a precaution, and the convocation was moved indoors.
Environment Canada said that for the Montreal area the worst is over and it lifted a severe thunderstorm warning advisory. Montreal and its surrounding area remains under a weather watch.