Utility companies across Ontario and Quebec worked to restore electricity this morning to more than 120,000 homes and businesses that were left in the dark by a line of severe storms.

Heavy rain and wind gusts of up to 90 km/h knocked down trees and power lines across southern Ontario and into Quebec's Estrie and Laurentian regions.

By Monday afternoon, some 57,000 Ontarians — down from 100,000 at the storm's peak — were still without power in Ontario, according to Hydro One.

Crews worked through the night to get the lights back on in Toronto though "small pockets" of the city were still without power by morning according to Toronto Hydro.

In Quebec, just over 1,000 were without power, down from more than 23,000.

Hydro-Québec spokeswoman Marie-Élaine Deveault said the strong winds snapped trees and branches, downing power lines.

She said crews are working on restoring power.

“They’ll [the crews] stay there as long as they have to,” Deveault said.

In the Montreal area, winds were gusting up to about 80 km/h, and just under 1,000 customers were without electricity.

Deveault said it’s too early to tell when all the power will be restored.

“The winds are still strong right now, so we’re following this situation,” she said.

The weather system roared into Ontario after punishing the American Midwest with tornadoes and thunderstorms that left at least six dead in Illinois.

In the central Illinois town of Washington, a twister obliterated entire neighbourhoods, flipping vehicles, uprooting trees, and ripping down power lines.

The storms also caused damage in Kentucky, Wisconsin, Indiana, Ohio and Michigan.