Canadian officials say as many as 27 people have died after a massive storm caused “one of the most destructive natural disasters in Canadian history”.
Six people were also missing, presumed dead.
Torrential rain in the province of Alberta caused flash floods, leaving one million residents of Alberta’s southern and central regions cut off by the floods.
The floods have led to a state of emergency in Canada’s second-largest province.
The rain pounded the area with speeds of up to six inches (15cm) an hour, reaching up to 200mm (8ins) in parts of southern Alberta.
Late on Thursday, the Canadian military was called in to help, with 600 troops replacing firefighters who had been working alongside the civilian search and rescue teams.
The Canadian Red Cross has raised more than $23m (£13.5m) in support of flood victims.
A spokesperson for the Canadian Red Cross told BBC News : “The floods have left the residents of Alberta with a huge amount of losses,” she said.
“The community is currently coming to terms with the losses and it will take time to recover.”
Canadian Prime Minister Justin Trudeau’s office said he would visit the province.
Alberta’s emergency management authority said on Friday that the missing six could be among the missing 27 who died.
Pictures posted by the authorities showed cars marooned in debris and pedestrians walking on flooded roads.
Helicopters carrying emergency crews flew over destroyed buildings and submerged homes.
Police rescued stranded residents from homes and from cars.
In Rocky Mountain House, about 70 miles (110km) west of Calgary, the local mayor described the floods as “the biggest one I’ve ever experienced”.
And in the city of High River, some 75 miles from Calgary, officials told residents to leave their homes, as a deep hole swallowed up a portion of the town centre.
Some people called the National Disaster Assessment Team (NDAT) from helicopters, some in ambulances, others in kayaks and canoes to report problems.
Ottawa for a time was directly in the path of the storm, and flash flooding was widespread in areas that are immediately adjacent to the cities.
In Calgary, where the flooding began, there is relief in sight.
Twenty-five percent of the city was affected, but the worst of the worst was over on Thursday night, according to Mayor Naheed Nenshi.
Mr Nenshi said the work of teams of volunteers would be repeated in coming days and hours.
He had repeatedly warned residents not to stay in flooded neighbourhoods after water levels started to rise.
The deaths toll was confirmed on Friday, after authorities were forced to stop searching for the missing.
Media outlets in Canada had earlier reported that the rainstorms killed 21 people in the province.
An official with the City of Calgary said on Thursday that at least 10 people had died in the province.
Lines at gas stations and restaurants were stretching for blocks as thousands of residents deserted their homes and stayed in emergency shelters.
“We were blown away by the event, but we are fortunate there have been no fatalities in the City of Calgary,” Mr Nenshi said.
“When the time comes, I think we’re going to look back and the people that died will be fitting,” he added.