This story was produced by Roof Gnome and reviewed and distributed by Stacker Media.
These US counties are most vulnerable to tornado damage
Which counties face the biggest risks of destruction in the path of a tornado?
With tornado season—March to June—upon us, Roof Gnome ranked 2024's most vulnerable counties for tornado damage.
We compared nearly 950 U.S. counties with a relatively moderate to very high tornado risk according to FEMA. More specifically, we looked at tornado risk and expected annual loss from tornadoes. We also considered the average age of homes and whether states have adopted construction codes for tornado resilience, among 5 total metrics.
To learn how we ranked the counties, see our methodology below.
The upshot
Twisters tend to strike in Tornado Alley, a nickname for the nation's central region with the most tornadoes from the 1950s to 1990s. 17 Texas, 12 Illinois, 9 Missouri, and 7 Kansas counties finished among the 100 most vulnerable counties for tornado damage due to high tornado incidence and financial risk.
However, tornadoes aren't confined to the historic Tornado Alley. Since 1989, tornado frequency has been increasing farther north and out east. 6 Michigan and 5 Ohio counties landed among the 100 most vulnerable counties in our ranking.
With large populations and high-cost infrastructure, counties with major cities have the highest total expected annual loss from tornadoes. 7 Texas counties — such as Harris (No. 2), Dallas (No. 16), and Bexar (No. 23) — finished among the 10 with the costliest expected annual loss from tornadoes. These are home to the Texas Triangle.
Missouri, Kansas, and Illinois stand out with high Exacerbating Factors. These states have many older homes and have not adopted current building standards from the International Residential Code and International Building Code. Building codes — like stronger roofs, safe rooms, and impact-resistant windows — help increase structural resilience against extreme weather events.
Behind the ranking
First, we determined the factors (metrics) that are most relevant to rank the Most Vulnerable Counties for Tornado Damage. We then assigned a weight to each factor based on its importance and grouped those factors into 3 categories: Incidence Risk, Financial Risk, and Exacerbating Factors. The categories, factors, and their weights are listed in the table below.
For each of the 946 counties with a relatively moderate to very high tornado risk according to FEMA, we then gathered data on each factor from the sources listed below the table.
Finally, we calculated scores (out of 100 points) for each county to determine its rank in each factor, each category, and overall. A county's Overall Score is the average of its scores across all factors and categories. The highest Overall Score ranked "Most Vulnerable" (No. 1) and the lowest "Least Vulnerable" (No. 946).
