One man is critically injured, homes have been damaged and hydro poles are down after a series of severe thunderstorms cut a swath of destruction through central and southwestern Ontario Friday.

Heavy rain and high winds hammered much of the region late Friday, knocking down trees and power lines in Orillia and the nearby Beausoleil First Nation.

A 51-year-old man was taken to hospital Friday night after he was found trapped under a fallen tree in Orillia. Police said Orillia city workers were removing the fallen tree when they found the man unconscious beneath it.

Parts of Orillia remain off-limits as city workers and emergency crews work to assess the damage caused by Friday's storm. Roads are blocked, hydro lines are down and some residents remain without power in the area.

Residents at the Beausoleil First Nation reported sightings of a possible tornado on Friday night. Several homes at the reserve have been damaged by fallen and uprooted trees, and many residents are still without power.

Environment Canada said later Saturday that damage in the area is consistent with a strong downburst of wind, not a tornado. A downburst is a sudden, strong column of air that blasts down and outward, sending air surging in all directions.

Wind speeds in the downburst are estimated to have been between 110 to 130 kilometres per hour.

Environment Canada says hail in the Orillia area on Friday afternoon was up to 28 millimetres in diameter.

Emergency crews continue to clean up the broken trees and disconnected power lines.

The cleanup is expected to take days.

The Beausoleil First Nation is located on Christian Island in Georgian Bay.

Elsewhere in Ontario, Environment Canada says wind damage near London, Ont., shows a tornado did not touch down in the area.

The heaviest rains fell in St. Thomas, a small city outside of London. Environment Canada says 124 millimetres of rain fell there until 10 p.m. on Friday.

Customers were evacuated from a St. Thomas shopping mall early Saturday after rain damage caused a portion of the roof to sag.

Environment Canada is predicting a warmer-than-usual fall season throughout Ontario. And Eastern Canada is expected to see a lot of violent weather in the coming weeks as the remnants of hurricanes move up the coast.