Tornado

A Tornado is a narrow, violently rotating column of air that extends from the base of a thunderstorm to the ground and is visible only if it forms a condensation funnel made up of water droplets, dust, and debris.

In the National Risk Index, a Tornado Risk Index score and rating represent a community's relative risk for Tornados when compared to the rest of the United States. A Tornado Expected Annual Loss score and rating represent a community's relative level of expected building and population loss each year due to Tornados when compared to the rest of the United States.

A map of the United States colored by Tornado Risk Index ratings. Tornado risk is possible across the United States and is most prevalent in the Midwest and southeast. For full results, see the National Risk Index Map webpage.

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Tornado Exposure

A Tornado exposure value represents a community's building value (in dollars), population (in both people and population equivalence), and agriculture value (in dollars) exposed to Tornadoes.

Tornado Annualized Frequency

A Tornado annualized frequency value represents the average number of recorded Tornado hazard occurrences (events) per year over the period of record (34 years).

Source Data

National Oceanic and Atmospheric Administration's National Weather Service's Storm Prediction Center's Severe Weather Database

Tornado Historic Loss Ratio

A Tornado historic loss ratio is the representative percentage of the exposed consequence type value (building, population, or agriculture) expected to be lost due to a Tornado hazard occurrence.

Tornado Processing Methodology

For comprehensive details about the Tornado processing methodology, see the National Risk Index Technical Documentation.

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