In Quebec, areas around Rigaud, Gatineau and certain regions of Montreal, states of emergency have been declared as hundreds have been evacuated.
Premier Philippe Couillard, who attended the Montreal news conference, said he understands the frustration many people are feeling.
Meanwhile, Goodale said no other province has so far requested military help, but forces personnel, including reserves, are on standby across the country.
"Providing relief and recovering from the aftermath of this disaster is going to be a long-term proposition, " Goodale said.
Quebec is now the hardest hit as military personnel have been called out to help with flood mitigation, By the end of today some 1650 military will be in various areas around the province, a lot of them in western Montreal.
"We will follow the fire department and actually remove the people if need be", Gruenwald said.
Two men carry belongings along a flooded street in the town of Rigaud west of Montreal, Sunday, May 7, 2017, following flooding in the region.
The Ottawa River splits Ontario and Quebec, and on the Ontario side the community of Clarence-Rockland declared a state of emergency because of rain levels.
"I strongly urge residents of le Mercier and other residents whose safety can not be ensured by emergency services to comply with the evacuation order", he said.
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City officials have described the flooding as the worst in decades.
Coderre said the situation was under control and the emergency response would be adapted to meet any changes in circumstance. The level of Lake Ontario was already at a 20 year high.
Heavy rainfall has pushed water levels in the region's creeks and rivers over their banks and led to major flooding.
Firefighters have been given extra resources to battle the spreading floodwaters.
The heaviest rainfall seems to have been in New Brunswick, where a weather station northeast of Saint John recorded 155mm of rain between late Friday and the early hours of Sunday.
"We might be in the week where the water will progressively begin to drop, but there's still a lot of work before us to deal with flooding after the water has receded", he said.
Warmer temperatures had caused snow to melt in British Columbia in Canada's West, combining with the rain to cause flooding and mudslides.
Waterways remain extremely precarious, he said, and people who get too close are at risk of being swept away by fast-moving water.
A 30-something man and a 2-year-old child are still missing after being swept away by a flooded river.