A firefighter walks near several power lines that were downed after a lightning strike in Winnipeg. (CBC)

Thunderstorms rolling through southern Manitoba on Thursday left power outages, flooded streets and downed power lines in their wake.

Booming thunder and flashes of lightning rocked the city of Winnipeg at about 4 a.m. and rain continued to fall in heavy sheets through the morning rush hour.

A lightning strike overnight put close to 900 hydro customers in Winnipeg's River Heights neighbourhood in the dark for about three hours. Not long after power was restored, another 700 customers were taken off-line by crews who had to make additional repairs.

Yet another strike in the same neighbourhood at about 9:30 a.m. caused power lines to fall and spark off parked cars in the area of Corydon Avenue and Centennial Street. Lines were also down in the back lane of Blanche Avenue in Tuxedo, said hydro spokesman Jim Peters.

'It was insane. It was like, I woke up at I don't know what time, and my tent was all over my face because the poles had snapped.'—David Skene, Folk Festival camper

In other parts of the city, manhole covers popped out of place because of the pressure of water in the storm sewer system. Traffic lights were either out or flashing red and city crews also responded to several calls about flooded basements and residents smelling sewer gas.

The torrent of water also led to untreated sewage runoff into the Red River, said city engineer Bill Watters, who is with the Winnipeg Water and Waste department. That happens when there's more water than the system can handle, he said.

"During a heavy rainstorm like this, the sewage system is designed so that instead of the sewage backing up into people's homes…the water will get discharged into the river."

The sewage runoff stops when water levels subside, Watters added.

Surgeries cancelled at Victoria General Hospital

Underpasses in many parts of the city were turned into deep pools while water seeped into sections of Victoria General Hospital, forcing officials to suspend 40 elective surgeries for the day and move patients to other areas in the building. About 33 elective surgeries scheduled for Friday have also been cancelled.

West of the city, traffic on highways was slowed and vehicles pulled to the shoulder as visibility dropped to almost nothing. And campers at the Winnipeg Folk Festival in Bird's Hill Park, about 10 kilometres northeast of the city, scrambled for cover as tents were blown down.

"It was insane. It was like, I woke up at I don't know what time, and my tent was all over my face because the poles had snapped," said festivalgoer David Skene.

He stayed at the site until another tent, which became airborne, collided with his. That's when he decided to leave the campsite for the morning until things cleared up. Skene planned to head back sometime in the afternoon.

Jeremy Campbell, a volunteer camping at the festival site, said walking around in the morning was like pushing through a monsoon. Despite all the water left behind, things returned to normal as soon as the clouds rolled out, he said.

"Not a lot of problems — people came out of thier tents and started their routines," he said.

Tamara Kater, the festival's executive director, said inclement weather is nothing new. Staff, campers and festivalgoers have dealt with it all before, and the show always goes on.

"Some of the rainfall amounts in west-central Manitoba have been over 50 millimetres. The shocking thing here is that it's happening in a real hurry. So, the rainfall rate is very high," said CBC meteorologist John Sauder.

The system eased up by late morning, but it might not be over entirely, Sauder said. A resurgence of storms could come in the afternoon once the temperature heats up again. There is also a chance of showers on Friday.