Around 2,500 homes in Huntsville and Bracebridge are in the dark. Hydro One says the areas of Livingston, McClintock, Ridout, Havelock, Franklin and Sherborbe are all affected.
The power has been out since around 11:30am and Hydro One says it expects it to be restored around 3:30pm.
The cause of the outage is still unknown.