On This Day: May 31, 1985 — The Only F5 to Hit PA
On the evening of May 31, 1985, a violent squall line crossed the Ohio border into Pennsylvania and dropped the only F5 tornado the state has ever recorded. Before sunrise, 44 tornadoes had carved across Ohio, Pennsylvania, New York, and Ontario, killing 90 people and injuring more than a thousand. The May 31, 1985 tornado outbreak remains the deadliest tornado day in Pennsylvania history and one of the strangest twister events ever to hit the eastern United States — a Plains-style assault on a region that was supposed to be safe from monsters like this.
Why a Plains-Sized Outbreak Hit the Wrong Region
Tornadoes happen east of the Mississippi every spring, but they do not usually arrive in this size or this strength. By dawn on May 31, an unusually deep area of low pressure sat over Duluth, Minnesota. A cold front trailed south through Illinois and Missouri while warm, moist Gulf air pumped north into the Great Lakes. By late afternoon Cleveland hit 87°F, Erie hit 85°F, and the dewpoint stayed punishingly high. A jet streak punched across the upper atmosphere at the worst possible moment, and a cap that had been pinning down the storms broke wide open.
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What followed was almost mathematically perfect for severe weather. Storm chaser folklore says you need shear, instability, and lift in the same place at the same time. The atmosphere over the Allegheny Plateau served all three at once. The first cells fired in eastern Ohio shortly after 4 p.m. Within an hour they were dropping wedges.
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