Parts of the West Edmonton Mall will stay closed for an undetermined time as insurance adjusters examine the damage from a severe hailstorm Sunday.

Mall general manager Gary Hanson said stores in most of the building were opening as usual on Monday morning, but the water park would open later in the day and the most badly damaged section of the mall will remain closed.

Hanson said it will cost millions to repair and clean up that section of the mall.

Sunday's storm damaged the roof and forced the evacuation of 30,000 people from the world's largest shopping mall.

Water was ankle-deep in parts of the 800-store mall after pipes on the second floor burst.

Tens of thousands of customers and employees streamed out into a flooded parking lot, where the water rose as high as waist level because ice from the hail had blocked storm sewers.

Kathleen Smith was in the mall's water park when the storm hit.

"The water was almost up to our knees in the change room, with raw sewage floating in the water," she said.

The mall's NHL-sized ice rink and indoor amusement park were flooded as sections of the roof ripped open under the force of the hail and pounding rain. Witnesses said they saw a waterfall flowing from the centre's second level.

Elsewhere in Edmonton, five apartment buildings also had to be evacuated because flooding in an underground parking lot had forced gasoline from the tanks of submerged cars, causing a fire and health hazard.

Hailstones ranging in size from golf balls to baseballs left a frosty coating of slush on lawns and sidewalks throughout Edmonton. Many streets were impassable by vehicle, leading people to wade through knee-deep water under a darkened, green-tinged sky.

Jeremy Levy was one of the many motorists who were stranded.

"I'm in three feet of water and my car is not going anyplace," he said. "This is July, might I add. Welcome to Edmonton."

There were reports of flash flooding as well, including one report of a 15-metre wide wall of water in the city's Laurier Park. As the water began to rise, people were forced to climb on top of picnic tables, and garbage cans floated away in the flood waters.

Sunday's deluge was Edmonton's third major rainstorm this month.

Adding to the weather misery on the weekend, forecasters also warned people to be on the lookout for tornadoes after witnesses spotted funnel clouds in two locations northeast of Edmonton.

One touched down near Andrew. The other one, near Morinville, lifted a garage and moved it 200 metres. A local farmer also reported a grain bin missing.

On Thursday afternoon, a tornado swept through Grande Prairie, about 450 kilometres northwest of Edmonton. No one was injured, but a car was flipped, hydro poles snapped and shingles were ripped from roofs.