People in low-lying areas of Medicine Hat are being advised to leave their homes

The South Saskatchewan River continues to swell and that has prompted police to implement a voluntary evacuation order.

The order affects 600 homes in an area of Medicine Hat called the Flats.

Andy McGrogan, assistant duty director for emergency services, said the evacuation notices were not mandatory but 44 families sought refuge in emergency shelters. The notices likely won't be lifted for some time, he added.

"Right now the things are stable and that's great, the sun's shining," McGrogan said. "Obviously the concern is what's going to happen with the rain."

The low-lying land of Medicine Hat is normally arid, making flooding unusual. But torrential rains across Alberta and Saskatchewan in the past few days has damaged homes and shut highways. As much as 150 mm of rain has drenched the region.

Jack Clark said he tried to carry out as many valuables as he could from the house of his neighbour, who was out of town as flood waters rushed into her home.

"It was running in the side door," he said. "It sounded like Niagara falls ... Unreal."

Leila Daoud, with The Red Cross, urged residents affected by the evacuation notices to register with the organization and leave their homes voluntarily, "while they can still take some basic items with them."

Environment Canada has issued a rainfall warning as another 30 mm of rain is expected in the area by Monday night.

Warnings are not usually issued unless 50 mm is forecast, but Environment Canada decided in light of the situation, the warning was warranted.

With files from The Canadian Press