Recently, an undergraduate in the Department of Atmospheric Science at the University of Illinois helped me look at the tornado statistics for Illinois. Among the things we plotted were the number of deaths and injuries reported in Illinois since 1950.
The first thing you will notice in both the deaths and injuries per year are the standout years of 1967 and 1990. The high numbers in 1967 were due to the Belvidere-Oak Lawn tornado outbreak of April 21, 1967. The high numbers in 1990 were due to the Plainfield tornado of August 28, 1990. As events have shown this year, despite our best efforts at warnings and preparations, an EF-4 or EF-5 tornado in an urban area will create significant casualties.
The second thing you will notice is that there are no upward trends in the deaths and injuries per year in Illinois despite our population increasing from 8.7 million in 1950 to 12.8 million in 2010. Some earlier research on Illinois tornadoes has shown that while we are detecting more EF-0 tornadoes (the weakest category) due to improved technology, we are seeing about the same number of EF-1 to EF-5 tornadoes through time.
By the way, the “EF” or “Enhanced Fujita” scale rates tornadoes from EF-0 (weakest) to EF-5 (strongest) based on damage. See Enhanced Fujita scale for more information.