Mayor Naheed Nenshi said the Elbow River, one of two rivers that flow through the southern Alberta city, has peaked.
And if things don't change, officials expect that the flow on the Bow River - which, in his words, looks like "an ocean at the moment" - will remain steady for the next 12 hours.
Nenshi said just over two dozen neighborhoods have been evacuated and most of the estimated 75,000 displaced people are staying with family and friends. There are about 1,500 people in evacuation centers in and around Calgary, a city of more than a million people that hosted the 1988 Winter Olympics.
Nenshi said earlier he's never seen the rivers that high or that fast.
Low-lying areas along the river started to flood Thursday night and there was water filling up some underpasses. There was water in the streets of the Bowness area in the city's northwest. The city has not said to what extent any homes have been flooded.
Police urged people to stay away from downtown and not go to work. All schools - both Catholic and public - are closed, while Catholic schools in the communities of Chestermere, Airdrie and Cochrane were also to be shuttered.
The Calgary Zoo, located on St. George's Island, closed its gates and started taking steps "to secure and move animals to safe locations."
Contingency plans called for big cats, such as lions and tigers, to be moved into prisoner cells at the Calgary courthouse. But the city said that hadn't happened yet.
It had been a rainy week throughout much of Alberta, but on Thursday the Bow River Basin was battered with up to 100 millimeters (4 inches) of rain. Environment Canada's forecast calls for more rain today in the area, but in much smaller amounts.
Calgary is not alone in its weather-related woes. There were flashpoints of chaos from Banff and Canmore and Crowsnest Pass in the Rockies and south to Lethbridge. More than a dozen towns declared states of emergency, with entire communities including High River and Bragg Creek under mandatory evacuation orders.
Some of the worst flooding hit High River, where it's estimated half of the people in the town have experienced flooding in their homes.
Military helicopters plucked about 31 people off rooftops in the area. Others were rescued by boat or in buckets of heavy machinery. Some even swam for their lives from stranded cars.
A spokesperson for Defense Minister Peter MacKay said about 354 soldiers are being deployed to the entire flood zone.
Prime Minister Stephen Harper promised Alberta Premier Alison Redford she'll have Ottawa's full support for rescue and recovery efforts.
Pictures from inside the mountain town of Canmore show a raging river ripping at the foundations of homes.
Near Black Diamond on Thursday, the Highwood River also swept away two people. One was found, but the second - a woman - is still missing.
Pictures from inside the mountain town of Canmore also a raging river ripping at the foundations of homes.
Bruce Burrell, director of the Calgary Emergency Management Agency, said water levels on the Bow River aren't expected to subside until Saturday afternoon.
"Depending on the extent of flooding we experience overnight, there may be areas of the city where people are not going to be able to get into until the weekend," he told a news conference.
Heavy rains eight years ago caused flood damage to about 40,000 Calgary homes and resulted in the evacuation of more than 1,500 residents. It resulted in $275 million in insured losses. Nenshi said this is worse.