Several locations in High River are under evacuation.
A large part of the town of High River is threatened by flooding, confirms High River RCMP.
Police are asking the public to refrain from driving to High River for their safety.
A mandatory evacuation has issued for several areas in High River as the Highwood River continues to rise. The hospital has been evacuated and residents of a seniors residence have been asked to leave.
High River Mounties are asking residents with motorboats to help rescue at least a dozen people stranded in their homes.
"It's bad," said High River spokeswoman Joan Botkin.
"The most unnerving thing, I guess, is that river forecasters are predicting - if we receive another 40 millimetres of rain - the Highwood will crest at about 1,270 cubic metres a second between noon and early evening. We encounter flooding at around 210 cubic metres."
Story continues after slideshow
Flooding In Southern Alberta, June 20, 21
Some highways and roads in the area, including parts of the Trans-Canada Highway, have been closed because of water or mud slides.
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.
With files from The Canadian Press
Follow updates on our live blog below: