Tropical storm Irene blew into Quebec midday Sunday, bringing high winds, heavy rains and power outages.
Quebec public security minister Robert Dutil urged Quebecers to take the storm seriously.
"It's important that people not take Irene lightly," Dutil said at a press conference Sunday in Quebec's Beauce region."This isn't a small storm, it's an enormous storm."
Emergency centres are set up in many high-risk regions, including the Eastern Townships, the Montérégie/South Shore, the Lower Saint-Lawrence and Quebec City. Officials were on call to provide information and assistance as needed.
The Trudeau airport recorded 65 km per hour winds Sunday afternoon, causing problems in Montreal, the Eastern Townships and beyond.
Traffic lights were knocked out across the island, with police directing traffic at dark intersections.
Wind gusts ripped off large tree branches in the Plateau, Verdun and NDG.
Hydro-Québec said at least 180,000 customers lost power in the city and beyond, including Montreal's NDG and the West Island, the Montérégie and the Eastern Townships. Power appeared to flicker on and off in some regions.
The Quebec government urged people to stay indoors until the storm passed.
Hundreds of U.S.-bound flights departing from Montreal, Quebec City and Toronto were cancelled over the weekend because of Irene.
Irene is a 'humongous' weather system
But the storm remains a "humongous weather system," said Frank Cavallaro, CBC Montreal's weather specialist.
"The cloud stretches as far west as Toronto, the London region, and as far east as Newfoundland. It's moving quite rapidly."
The Canadian Hurricane Centre says although Irene has been downgraded to a tropical storm, it still has the potential to cause flooding and wind damage to parts of eastern Canada.
Centre director Chris Fogarty says the heaviest rainfall is expected in Quebec's Eastern Townships, with forecasts predicting 100 mm of rain in the next 24 hours.
In Montreal, Laval and the South Shore, 50 mm could fall.
The centre of the storm is expected to push over the Gaspé region and St. Lawrence River Valley on Monday.
Environment Canada has issued wind and heavy rain warnings for southern and eastern Quebec.