A severe thunderstorm warning has ended for most of Southern Ontario but remains in effect for areas including North Durham and the Kawartha Lakes.

Environment Canada warns that the storms could bring torrential rain in excess of 50-75 mm.

Deerbourne/Deerfield will be blocked off due to severe weather please avoid area. <a href="https://t.co/EOrBpn8J9d">pic.twitter.com/EOrBpn8J9d</a> —@PeelPoliceMedia

The storm downed trees and wires in parts of Toronto and the surrounding areas. Multiple power outages were reported across the city, Toronto Hydro said Saturday.

Pam Ogawa was in her boat when what she believes is a tornado hit in Pefferlaw, Georgina.

"I didn't know what it was at first… It was just whistling and I just thought, 'That's not right.'"

"I'd never experienced anything like that. I'm shaking like a leaf. It was so loud - it was like a whistling. I couldn't even hear anything."

She says she's now waiting for the rain to stop so she can get her belongings off the boat and leave.

<a href="https://twitter.com/hashtag/Toronto?src=hash">#Toronto</a> dt is about to be # pummeled by huge <a href="https://twitter.com/hashtag/ONstorm?src=hash">#ONstorm</a> <a href="https://t.co/5K0CRE7jyV">pic.twitter.com/5K0CRE7jyV</a> —@Dick_Lefty77

Environment Canada says the storms could also bring brief strong wind gusts and heavy downpours that could cause flash floods and water to pool on city streets. Lightning is also possible.

"Remember, when thunder roars, go indoors!" it said in a statement on its website.

My view from here 😁 <a href="https://twitter.com/hashtag/tostorm?src=hash">#tostorm</a> <a href="https://twitter.com/hashtag/onstorm?src=hash">#onstorm</a> <a href="https://twitter.com/hashtag/summerstorm?src=hash">#summerstorm</a> <a href="https://twitter.com/hashtag/toronto?src=hash">#toronto</a> <a href="https://t.co/fOQMTKg0VH">pic.twitter.com/fOQMTKg0VH</a> —@blogspotgirl

Meanwhile, a tornado warning has ended for the Ontario towns of Newmarket and Georgina, the township of Uxbridge and the community of Beaverton.The warning also applied to northern York Region and northern Durham region but it is now over.

LIVE on <a href="https://twitter.com/hashtag/Periscope?src=hash">#Periscope</a>: Storm Chasing Central Ontario <a href="https://t.co/GmzcBRgYR7">https://t.co/GmzcBRgYR7</a> —@vaughanweather

Earlier Saturday, an eyewitness had reported a tornado on the ground at Sunset Beach on the southeast shore of Lake Simcoe at 12:50 p.m. The report has not yet been confirmed.