Horizon Utilities said some 30,000 customers were affected by a widespread power outage in St. Catharines Saturday afternoon.
The power went out shortly after 2 p.m., and crews were dispatched to restore service.
Horizon said the cause of the outage was a supply problem from Hydro One.
Shortly before 3 p.m., power began to be restored in various areas of the city, and at 3:45 p.m. Horizon said power had been fully restored to St. Catharines.