May 31 : Below 350 PPM

May 31, 1985

A vicious tornado outbreak struck southern Ontario, central and eastern Ohio, western and central Pennsylvania, and western New York. 42 tornadoes ripped through the area. 88 people were killed and total damage was over $200 million. 8 of the tornadoes were rated F4 on the Fujita scale. The tornado that devastated Niles, Ohio was classified as F5 (winds above 260 mph). A huge F4 tornado had a 69 mile path length in central Pennsylvania, mostly through Moshannon State Forest. An estimated 88,000 trees were destroyed as the tornado’s path width reached 2.2 miles at one point.

Tornado warning issued for St. Louis area | Fox News