Spokeswoman Nancy Shaddick says high winds ahead of a cold front moving across the province were responsible for the outages.
A wind warning covering the Parry Sound, North Bay and Kirkland Lake areas was issued, with gusts up to 90 kilometres an hour expected.
As of 6 p.m. Oct. 14, Hydro One's website reported about 2,200 customers remained without power, down from 13,000 earlier in the day.
Shaddick says the hardest hit areas were Sudbury and Timmins, but Manitoulin Island, Kapuskasing, Kirkland Lake, Parry Sound and Huntsville also saw significant outages.
Shaddick says most customers could expect service restored by evening, with more remote residents perhaps not seeing power restored until 9 p.m.