A severe thunderstorm early Thursday morning flooded streets, yards, basements and construction sites in Edmonton.

Sections of Whitemud Drive were underwater at 111th Street west of Calgary Trail. City workers arrived shortly after 7:30 a.m. to begin clearing the water. To the chagrin of commuters, the road did not reopen until noon.

Dharminder Gill told CBC News he was driving to work at 3 a.m.when his car stalled in the rising water. Within five minutes the water was waist deep, he said, and when he opened his window to escape the water began pouring in.

"I was scared," he said. "I took my bag and ran through the water and moved to a safe place."

Dharminder Gill's car became trapped on Whitemud Drive. (Andrea Huncar/CBC)

The normally busy Mill Woods intersection at 66th Street and 34th Avenue was also flooded.

Firefighters spent much of the morning rescuing people from swamped vehicles, with at least 18 cars trapped due to the rainstorm, and responding to alarms set off by the storm.

"We had over 70 calls in a short period of time," said fire Chief Ken Block, adding the calls left some areas of the city without direct fire coverage. "At a point last night we had crews from downtown responding in Mill Woods, which is a long ways away."

Some off-duty firefighters had to be called in to bolster resources, he said.

Firefighters also responded to two house fires caused by lightning strikes, each with roughly $100,000 in damage, Block said. "Our resources were stretched very thin."

Epcor reported 15 electrical circuits knocked out by lightning, though most power was restored by 8:30 a.m.

Many homes and vehicles were flooded in Mill Woods and other southside communities.

Millwoods Recreation Centre, except for the arena space, will remain closed until at least Monday because of flood damage.

Floating refrigerator

Chris Kucher awoke to find water flowing in through the front door of his basement apartment.

Hailstones from Thursday's storm are shown next to a ping pong ball. (Chris Biensch)

"I was kind of in shock," he said. "I grabbed a towel and threw it down and I was like, 'This is stupid, it's not going to do anything.'"

By 4:30 a.m. everything including his refrigerator was floating in water, he said.

Wilbert Miller from Fort McMurray was visiting a friend in Edmonton when the storm hit.

"I called my buddy and said, 'Hey, man. Something is floating away there,'" he said. "I'm thinking, 'Where's my car? How did my car get there?"

Wendy Clara had to dig out her shovel to remove the hail that had accumulated in her yard.

"And I had to hammer it," she said. "It was so hard."

AMA Insurance said it had received 100 claims of flooded basements and other damage from Riverbend to Millwoods by mid-afternoon.

Edmonton Public Schools said 12 schools reported storm damage, which ranged from minor water seepage to severe flooding caused by debris plugging drains in and around the schools.

Both the large and small gym floors at J. Percy Page High School in Mill Woods will have to be replaced because of water damage. The school also had flooding in the woodworking and automotive shops, cosmetology lab and music room.

Another Mill Woods school, T.D. Baker Junior High School, will also need a new gym floor. The repairs are estimated to take until the end of September.

Radar showed the large storm cloud that dropped the heaviest rain and hail was moving fast, said CBC meteorologist Cory Edel. The storm entered from the west at 4:09 a.m. and left to the east at 4:30 a.m.

"There was some lighter rain surrounding this storm but this was when the bulk that caused the flooding fell," he said. "With such large amounts falling in such a short span of time, flooding is inevitable."

Environment Canada pegged the amount of precipitation at 70 millimetres, though there are unconfirmed reports of 100 millimetres falling in some places. This amount of rain at one time is rare, though a storm on July 11, 2004, dropped an extraordinary 200 millimetres.

The severe weather for northern Alberta may not be over. Environment Canada issued a tornado watch for the area northeast of the Edmonton region early Thursday afternoon.

The heat wave that helped generate the storm will continue Thursday with a high of 30 C.