There are reports of downed trees, damaged buildings and fallen hydro wires after storms ripped through areas north of the city.
Photos from Collingwood show the roof a building torn completely off.
Severe thunderstorm watches and warnings were issued for areas around Lake Simcoe, as well as further to the southeast, including Northern York and Durham regions.
The severe weather is not expected to hit the city of Toronto.
Ronell Crescent in #Collingwood closed for a gas leak. No traffic allowed. pic.twitter.com/haFcxBp3iX
— TheConnection (@connectioncwood) October 17, 2016