Freezing rain and thunderstorms pummeled parts of Ontario and Quebec on Wednesday, knocking out power for about 800,000 people, officials reported.

Quebec’s power utility said shortly after 5 p.m. that more than 676,000 of its 4.5 million customers had no electricity as much of the province remained under a freezing rain warning.

“What’s causing the outages is the mixture of precipitation and wind,” Hydro-Québec spokeswoman Gabrielle Leblanc said. “It weighs down the vegetation. There can be branches and trees that fall on the lines.”

In Montreal, more than 316,000 customers had lost power, while 171,000 people were hit with outages in the Montérégie region, south of the city.

Leblanc said many of the outages were small in area, each affecting only a few customers, so crews would need to repair numerous breaks to restore power to everyone.

In Montreal, there were numerous reports of downed trees. Transport Quebec said weather conditions forced it to close the Victoria Bridge, which connects Montreal with its southern suburbs.

Public Security Minister François Bonnardel said his department has put a coordination center in place to deal with the storm.