The 1985 United States–Canada tornado outbreak, referred to as the Barrie tornado outbreak in Canada, was a major tornado outbreak that occurred in Ohio, Pennsylvania, New York, and Ontario, on May 31, 1985. In all 44 tornadoes were counted including 14 in Ontario, Canada. It is the largest and most intense tornado outbreak ever to hit this region, and the worst tornado outbreak in Pennsylvania history in terms of deaths and destruction.