Officials with the City of Calgary say as many as 100,000 people could be forced from their homes due to heavy flooding.
Mandatory evacuation orders have been issued for the communities of the Beltline, Bridgeland Industrial Area, Chinatown, Deer Run, Hillhurst, Quarry Park, Riverdale, Windsor Park, Sunnyside, Riverbend, Bowness, Westmount, Montgomery, Mission, Elbow Park, Stanley Park, Roxboro, Rideau, Discovery Ridge, Eau Claire, Downtown, East Village, Bonnybrook, Stanley Park, Elboya, Inglewood, Erlton, Cliff Bungalow, Victoria Park.
The city of Calgary has declared a state of emergency as expected heavy rainfall and incoming high river flows become severe.
The weather is also expected to impact Calgary Transit service during the Friday morning commute.
Residents facing evacuation are advised to find accommodation with friends or family for a minimum of 72 hours.
Reception centres have also been set up at Southland Leisure Centre and at Acadia Recreation Complex for those looking for alternate accommodation.
Emergency responders are going door to door in these communities and Calgary Transit is on standby to help evacuation efforts.
People are advised to take critical personal items such as glasses or infant needs along with identification.
The Calgary Zoo has also been closed due to high risk of flooding. Established emergency protocols are being followed to ensure safety of all animals, the Zoo said in a press release.
"Water is headed toward Calgary. We can expect more rain in coming days," said city officials on Twitter.
The city is implementing its flood response plan with the deployment of sandbags and temporary dams to protect property and infrastructure.
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Calgarians are advised to stay away from rivers and creeks as rising water may makes banks unstable.
Driving through flooded areas such as underpasses or children playing near storm water ponds and drains should also be avoided.
The state of emergency comes after the town of Canmore is drenched by heavy rain and flooding.
Heavy rainfall and lightning overnight Wednesday also resulted in power outages and flashing traffic signals in every area of the city of Calgary. Crews were out Thursday trying to repair the damage.
Environment Canada has issued a rainfall warning for the area, estimating as much as 100 millimetres of more rain could fall in the next two days.
The rainfall warning extends for much of southwestern Alberta, including Canmore, Banff, Calgary, Airdrie, Crowsnest Pass, Nordegg, Okotoks and Rocky Mountain House.
More updates on our liveblog below.
With files from The Canadian Press