By State › Illinois

Illinois: Overview

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Everything in the main manual and the skill guides applies in Illinois exactly as written. What’s different here is the specific hazard profile and the state, local, and legal context around it. This page is the starting point; the other three pages under Illinois go deeper on laws, local resources, and the data behind the risks named here.

Tornadoes: the deadliest single tornado in U.S. history passed through here

The Tri-State Tornado of March 18, 1925, remains the deadliest tornado in recorded U.S. history, and Illinois bore the overwhelming majority of it: 588 of the storm’s 695 total deaths were in Illinois, more than 100 of them in the town of Murphysboro alone. That event is a century old, but the risk isn’t historical: the November 17, 2013 outbreak, 77 tornadoes across the state in a single day, killed 8 people and caused $1.6 billion in damage, the deadliest and costliest November tornado outbreak in Illinois history. See the Risks page for the full data on both.

Earthquake risk from a fault system most people don’t associate with the Midwest

Southern Illinois sits at the northern edge of the New Madrid Seismic Zone, a major fault system running through the central Mississippi Valley. The USGS puts the 50-year chance of a magnitude 6 or larger earthquake in the zone at 25-40%, and communities in Illinois’s southernmost counties, Cairo, Carbondale, and Harrisburg among them, carry meaningfully elevated risk compared to the rest of the state.

Extreme cold: a record that still stands

In January 2019, a polar vortex event pushed Illinois to its coldest recorded temperature ever, -38°F in Mt. Carroll, and killed 3 people in Chicago alone as part of a Midwest-wide death toll of at least 21. Illinois hospitals treated 144 people for cold-related injuries in a single three-day stretch.

What this means for how you use the rest of this manual

The manual’s Tier structure and the skill guides apply without modification. What’s different in Illinois: tornado season planning (a safe room or basement, a NOAA weather radio, a practiced shelter plan) matters statewide, not just in a narrow “Tornado Alley” corridor; households in the state’s southernmost counties should treat earthquake preparedness as a real consideration, not an afterthought; and extended extreme-cold planning, backup heat, insulated pipes, a plan that doesn’t depend on the power grid staying up, deserves the same weight winter storm planning gets in states further north.

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