(CNN) -- Rivers fed by torrential mountain rains spilled across the prairies of southern Alberta, Canada, Friday, leaving two people dead and covering downtown Calgary in brown floodwater.
The two victims were caught up in the river that runs through the town of High River, about 40 miles south of Calgary, said Sgt. Josee Valiquette of the Royal Canadian Mounted Police. The two people have not been identified; a third person, a woman, remains missing.
High River is one of several communities where residents have been evacuated because of the flooding. Red Deer, 90 miles north of Calgary, and Lethbridge, about 130 miles to the south of the city, also have evacuations in place.
About 10,000 people in Medicine Hat, in southeastern Alberta, were being evacuated Friday ahead of the expected cresting of the South Saskatchewan River on Saturday, city spokeswoman Brandy Calvert said. That's about one-sixth of the city's 62,000 residents, she said.
Officials expect Saturday's flood to surpass the one they had in 1995, which was the biggest on record, Calvert said.
In Calgary, Mayor Naheed Nenshi said the Bow and Elbow rivers were carrying as much three times as much water through Calgary as they did during the city's monstrous 2005 flood, which obliterated roads, chased residents from their homes and drowned livestock on the way to causing more than $400 million in damages.
"The Bow River looks like an ocean at the moment," he said.
Canadian Prime Minister Stephen Harper toured affected areas by helicopter Friday afternoon along with Alberta Premier Alison Redford and Nenshi.
"Difficult day seeing so much devastation in southern Alberta, but encouraged by resilient spirit of so many Albertans," Redford tweeted. She said Harper pledged federal support.
Redford gave her condolences to the families of the flood victims and urged Albertans in flood-affected areas to stay safe.
In Calgary, the 17,000-seat Saddledome -- home to the NHL Calgary Flames -- was flooded, along with parts of Calgary Zoo and the Calgary Stampede grounds, where the famous annual Calgary Stampede rodeo is scheduled to take place in less than two weeks.
At the zoo, on the bank of the Bow River, staff moved the pot-bellied pigs and zebras to a safe location off-site. The zoo said the other animals were moved to higher ground.
As of Friday night, 25 neighborhoods in Calgary including most of downtown, were evacuated. They were also without power after the city ordered ENMAX, the energy utility, to shut it off in evacuated areas.
Clean water continued to flow to homes, but the city asked residents to limit their use as much as possible.
Residents in Calgary seemed alternately shocked by the flooding and willing to take it in stride.
"I don't think anybody's ever seen water flow through the streets," Calgary resident Rylan Broadbent told CNN Friday after evacuating his apartment building in the Erlton neighborhood, next to the overflowing Elbow River.
Others were more melancholy about the scope of the flooding, which forced more than 75,000 residents out of their homes and left the heart of the city largely deserted.
"We're not out of the woods yet," Neala Barton, the spokeswoman for the Alberta government, told CNN.
Some shelters in the city were filled to capacity, Calgary officials said Friday. Schools were closed.
Officials said most of the city's many bridges were holding against the water, but at least one was under water and another had washed out.
Still, the city's director of roads reassured residents the bridges are safe.
"The piers, the abutments on either side of the bridges, are right down to bedrock. What that means is what they are standing on is absolutely tied to the ground," Ryan Jestin said in a video posted on the city's website, standing in the rain overlooking the flooded Bow River downtown.
Meanwhile, Calgary police said they were patrolling evacuated areas to ensure that vacant homes and businesses would remain as safe as possible.
Authorities declared a state of emergency in several cities, including the mountain town of Canmore, where on Thursday, raging water tore out a portion of the Trans-Canada Highway.
Rescue crews used heavy construction equipment to rescue people from homes and businesses Thursday in High River, the network reported.
Canada's military was pitching in with helicopters and other assets to help local officials with rescue and evacuation efforts, Prime Minister Stephen Harper said.
The flooding was caused by a slow-moving storm that dumped 154 millimeters (more than 6 inches) of rain on the region from Wednesday to Thursday, CNN meteorologist Sherri Pugh said. As much as another inch of rain, about 25 millimeters, is possible northwest of Calgary on Friday, and yet another front is expected Monday, bringing the threat of more rain.
Calgary, near the Canadian Rocky Mountains, is perhaps best known for its rodeo, held each July. More than 1.4 million people attended last year, organizers say.
This year's Stampede events are due to begin in 13 days. It was unclear if the flooding would affect the event, but organizers did say on their website that other events scheduled at the park where the Stampede is held have been canceled through Sunday.
Calgary authorities are using the park as a staging area for flood response efforts.