May 31st is the deadliest day in Pennsylvania history due to the 1889 Johnstown flood and the 1985 tornado outbreak.
Flooding occurred days before in downtown Johnstown with The U. S. Army Corps recording 6-10 inches of rainfall. This ultimately lead to the failure of The South Fork Damn around 3:00 PM on May 31st, 1889.
When it failed a wall of water, as tall as 40 feet high, created a path of destruction down the Little Conemaugh River to Johnstown at a speed of 40 MPH.
The 14 mile path of destruction lead to 1,600 destroyed homes and 2,200 lives lost; 396 of which were children. Some bodies were found as far away as Cincinnati, Ohio.
On May 31st, 1985 43 tornadoes developed over Ohio, Pennsylvania, and New York. The strongest tornado was an F-5 and formed in Ohio and moved into Wheatland, Pennsylvania. The path was 47 miles long and lead to 18 deaths. Overall, the day lead to 1,000 injuries and 89 deaths.