Mayor Denis Coderre has declared a 48-hour state of emergency in Montreal.
Across the country, thousands of Canadians are spending the weekend in a desperate struggle with rising floodwaters caused by unusually persistent rainfall.
Floodwaters in Quebec are expected to peak Sunday due to continued rain in most of the affected areas. In total, nearly 1,900 homes are flooded in 126 municipalities in the province.
Public Safety Minister Ralph Goodale said Sunday that the military response to flooding in Quebec is likely to balloon.
"At the moment, since yesterday, there are 450 Canadian forces personnel on the ground in various locations across Quebec," Goodale told CTV's "Question Period."
"The expectation is that by the end of the day today that number will likely have tripled as the Canadian forces add more and more resources to assist the civilian authority in Quebec."
Goodale said no other province has so far requested military help, but forces personnel, including reserves, are on stand-by across the country.
The situation in Ontario seems to be "generally stabilizing," although there are many unstable local circumstances, he said.
Rob Kuhn, an Environment Canada meteorologist based in Toronto, said Sunday that eastern Ontario saw the most rainfall in the province. He added that upward of 80 millimetres of rain fell between Friday and Sunday morning in the Trenton area.
And though the rainfall has started to die down, another Environment Canada meteorologist, Bruno Marquis in Montreal, said much of Quebec should still expect another five to 10 millimetres Sunday.
The small town of Rigaud, west of Montreal, was among the hardest hit by flooding, and a state of emergency has been in place for several days.
Mayor Hans Gruenwald Jr. said the town is issuing a mandatory evacuation order.
He told reporters at a town hall Sunday morning that firefighters will be going door to door to make sure people in the affected areas leave their homes.
"We will follow the fire department and actually remove the people if need be," Gruenwald said. "Because it is either that or services will be stuck to remove those people under a state of emergency at two o'clock in the morning on a stretcher -- I'm sorry but we are not going to go there."
Meanwhile, Montreal Mayor Denis Coderre said the city is evaluating whether to declare a state of emergency after three dikes gave way in the Pierrefonds-Roxboro borough, in the north end of the city by the Rivieres des Prairies.
Homes have been evacuated in that borough as well as on the two nearby islands, Ile-Bizard and the smaller Ile-Mercier.
Coderre says the city has 30 Canadian Forces personnel helping firefighters and other emergency responders with the flood response.
"We have over 100 firemen who are working 24 hours a day, visiting door to door and making some evacuations," Coderre said.
Quebec Premier Philippe Couillard visited the town Saturday and urged people to heed authorities if they recommend they leave their homes.
In Atlantic Canada, some parts of New Brunswick recorded more than 150 millimetres of rain after a nearly 36 hour non-stop downpour.
A weather station northeast of Saint John, N.B., measured 155 millimetres of precipitation from late Friday to early Sunday, Environment Canada meteorologist Stephen Fougere said Sunday, adding that surrounding areas had up to 125 millimetres.
While the deluge has tapered off in the province, New Brunswick's St. John River is spilling its banks, prompting several road closures.
"It's above flood stage in several areas from Fredericton down south," Robert Duguay, a spokesman with the province's emergency measures organization. "Water levels are going to stay high probably for the rest of the week."
Without the added risk of snow melt or ice pack on the river from up north, he said the situation is under control with only minor flooding.
Still, Duguay said a shift in weather patterns could quickly change the situation. Waterways remain extremely precarious, he said, and people who get too close are at risk of being swept away by fast-moving water.
In British Columbia, rain combined with warm temperatures have accelerated the melting of the snowpack, which has resulted in flooding and mudslides throughout the province.