Powerful storms moved across southern Ontario Friday afternoon, ripping limbs from trees and downing power lines.

A rare tornado warning was issued in Toronto and other centres as a twister reportedly touched down in Fergus, Ont., near Guelph.

As much as 10 centimetres (3.9 inches) of rain fell in some parts of the Greater Toronto Area.
Storm sewers backed up, leaving motorists stranded in flooded streets during the evening rush hour.

"We've got standing water on the roads three-quarters of the way up on to hubcaps," said Geoff Coulson, a meteorologist with Environment Canada.

For most of the afternoon, officials at Toronto Pearson International Airport were telling travellers to anticipate delays and to check the status of their flights.

One volunteer storm spotter reported a tornado in the north part of Toronto but the report couldn't be corroborated by Environment Canada.

The government agency sent a team to Fergus to investigate reports a tornado damaged a home and toppled trees there.

In Guelph and Orangeville, trees reportedly knocked down power lines, leaving 10,000 residents without power.

"We're not sure what all the damage is yet because we're still patrolling the lines and assessing the damage," Hydro One spokeswoman Kathleen Welsh said late Friday afternoon.

It was unclear whether the lines had been downed by a tornado or strong winds.

Earlier in the day, buildings were reportedly damaged and cars overturned in the Kitchener area.

"The rain got heavier and heavier, and the wind kept changing direction," area resident Corey Heimpel told CTV.

In London, Ont., police reported seeing what seemed to be a tornado touch down in the area.

The storm system originated south of the border, in the American Midwest.

Earlier Friday a twister struck a town in south-central Wisconsin, levelling 15 homes and damaging 30 others.

A 54-year-old man apparently died of injuries sustained during the collapse of his home in Pleasant Springs, Wisconsin.

The U.S. National Weather Service was investigating reports of 18 possible tornadoes around the state.