Parts of Innisfil, south of Innisfil Beach Road, and areas of Bradford are without power after a collision involving a transport truck took out the main Hydro One feed, west of Highway 400.
Hydro One has suggested that it could take until about 3 p.m. for power to be restored.
"We're waiting for Hydro One" to complete the repairs, said staff at InnPower, Innisfil's utility company.
Power is also out in the Thornton area.
Motorists are reminded to treat flashing or non-functioning traffic lights as an all-way stop.
For more information on outages in Innisfil, visit www.innpower.ca/outages.php or check InnPower on social media.