A tornado is a violent windstorm characterized by a twisting, funnel-shaped cloud. It is spawned by a thunderstorm (or sometimes as a result of a hurricane) and produced when cool air overrides a layer of warm air, forcing the warm air to rise rapidly. The damage from a tornado is a result of the high wind velocity and wind-blown debris. Tornado season is generally March through August, although tornadoes can occur at any time of the year. They tend to occur in the afternoons and evenings: over 80 percent of all tornadoes strike between noon and midnight.

Tornado statistics from 1950 to 1995

State	Tornadoes	Deaths	Injuries	Cost
Ohio Totals	656	173	4156	$969,000,000
Ohio Avg/Year	14	4	90	$21,058,976
New York Totals	255	21	176	$194,690,688
New York Avg/Year	6	0	4	$4,232,406
Pennsylvania Totals	457	77	1077	$615,043,584
Pennsylvania Avg/Year	10	2	23	$13,370,514
W. Virginia Totals	83	2	90	$21,638,544
W. Virginia Avg/Year	2	0	2	$470,403
Kentucky Totals	403	105	2341	$287,000,000
Kentucky Avg/Year	9	2	51	$6,234,380
Indiana Totals	897	221	3665	$1,650,000,000
Indiana Avg/Year	20	5	80	$35,874,624