It was raining pretty hard and the wind start to pick up, so Pam Ogawa started folding up her outdoor furniture.

She ran onto her boat and "all of a sudden I heard the wind come up and it was so loud I had to cover my ears. And everything was blowing … and like a domino effect the roof started dropping and it just stopped just before my boat."

Ogawa was at a marina on the south shore of Lake Simcoe near Pefferlaw, Ont. She, like many other southern Ontario residents who took to social media Saturday afternoon, believe that a tornado struck the area.

"I had to run off my boat and I had to run into my husband's truck," she said. The structure over top of the boat in her photos is a metal roof held up by beams.

Oshawa residents also reported possible tornado sightings:

It is up to Environment Canada to determine whether storm activity constitutes a tornado.

Peter Kimbell, a warning preparedness meteorologist with Environment Canada, told CBC News that "we haven't a made a decision to send anybody out to investigate yet."

Kimbell explained that the department sends someone out in cases where there are "clear indications" of severe activity, including injuries, fatalities and major property damage.

Saturday's storms fall into a "grey area," Kimbell said, and Environment Canada will decide by the end of the day whether to make a determination about whether one or more tornadoes touched down.

While there is still thunderstorm watch in effect late Saturday afternoon, the worst of the weather had moved east of the GTA, he said.