Farther north, a cold front over far northwestern Ontario will force the development of several rounds of additional thunderstorms as it cuts into the hot and humid air across the region. These storms will start as clusters before growing into a line along the cold front.

Severe storms swept across Ontario Thursday, cutting power to thousands and toppling trees and power lines. Officials are investigating reports of a possible tornado near Stratford.

Severe thunderstorm warnings rumbled across eastern Ontario and western Quebec from about 6:30 to 10:30 p.m. When the storm was at its worst, it produced a tornado warning around Sharbot Lake, gusts of wind up to 90 km/h and lightning,