Schools and government buildings have been closed in some areas as the province grappled with the worst flooding in decades.
"Quebec and Ontario asked for military support and we're happy to give it and of course the federal government will assume all the costs related to support for Quebec and Ontario in these floods".
Almost 2,000 homes have been flooded in 126 affected towns and cities, with authorities urging residents to evacuate before it is too late.
Montreal Mayor Denis Coderre said about 220 people in the city had been evacuated from their homes.
Approximately 800 additional soldiers were deployed in Quebec on Sunday, the Canadian military said in a release. He said the problems will last for a number of weeks.
For many residents who have been fighting an exhausting battle to hold back the waters, often in vain, despair has started to set in.
Transport minister Laurent Lessard said the nine dams and reservoirs along the Ottawa River basin are structurally sound, but are being used to their maximum to try and slow the flow of water.
Ten towns have declared a state of emergency, including the province's largest city, Montreal.
"I have never seen so much water between Ottawa and Montreal", Sophie Gregoire-Trudeau, the wife of the prime minister, told broadcaster RDI.
Stewart says that's because it's a fairly new product that wasn't available prior to 2013, when severe flooding hit Toronto and Alberta.
According to the latest figures, 171 municipalities in Quebec are affected by flooding and 2,733 houses are flooded.
"Most interesting for me is to hear from the civilian authorities, as I met them in Montreal and now Rigaud, to get a sense of the response, how much more work to be done, do we need to reinforce at all, " Vance said.
Floodwaters in the province are expected to peak today due to continued rain in most of the affected areas.
A small town of Rigaud, west of Montreal, issued a mandatory evacuation order on Sunday. Water had built up on the road where they were driving and pushed the vehicle into the Ste Anne river last night around 6pm.
Quebec Premier Philippe Couillard also addressed the public via Facebook from the Gaspé region.
High water levels also forced Transport Quebec on Sunday night to close the Galipeault Bridge linking the western tip of Montreal with Île-Perrot.
Meanwhile, in British Columbia on the opposite side of the country, the same combination of rain and snow melt had caused flooding and mudslides that left at least two people missing, media reports said.
The province's environment minister says the historic flooding is the result of a harsh winter followed by heavy rains in April and May.