Power lines have been downed and houses washed into the sea after Storm Fiona battered Canada's coastline.
One woman is missing after being washed out to sea in Newfoundland.
Fiona was downgraded from a hurricane to a tropical storm on Friday. Such weather events are rare in Canada, and police said the storm was "like nothing we've ever seen".
The military has been deployed to Nova Scotia to help with the clean-up operation.
Parts of five provinces experienced torrential rain and winds of up to 160km/h (99mph), with widespread flooding and hundreds of thousands of people left without power.
Prime Minister Trudeau says the military will be deployed to Nova Scotia, adding: "If there is anything the federal government can do to help, we will be there."
He has said he will no longer travel to Japan to attend the funeral of former Prime Minister Shinzo Abe to deal with the storm's aftermath.
Tropical storm warnings have been issued for the Atlantic provinces of Nova Scotia, Prince Edward Island, Newfoundland and New Brunswick, as well as in parts of Quebec.
In Port aux Basques, with a population of 4,067 on the southwest tip of Newfoundland, intense flooding saw some homes and office buildings washed out to sea, local journalist Rene Roy, told CBC. The area is under a state of emergency.
"This is hands down the most terrifying thing I've ever seen in my life," Mr Roy said.
He added that many homes were left as "a pile of rubble in the ocean right now", adding: "There is an apartment building that's literally gone. There are entire streets that are gone."
Officials later confirmed that at least 20 homes had been lost.
The Royal Canadian Mounted Police said a woman was rescued after being "tossed into the water as her home collapsed" in the area.
Another report of a women being swept out from her basement had been received, they said, but conditions remained too dangerous to conduct a search.
Power companies have warned that it could take days to restore electricity, as wind speeds remain too high to start work on downed power lines.
Severe hurricanes in Canada are rare, as storms normally lose their energy once they hit colder waters in the north and become post-tropical instead.
Nova Scotia was last battered by a tropical cyclone in 2003 with Hurricane Juan, a category two storm that killed two people and heavily damaged structures and vegetation.
Fiona had already wreaked havoc on Puerto Rico and the Dominican Republic earlier this week, with many still left without power or running water.
Florida also faces a hurricane threat as tropical storm Ian strengthened as it moved over the Caribbean on Saturday. It could approach Florida early next week as a major hurricane.
