How we check facts

Every number on HazardFacts comes from a public federal data set. Each claim on a page links to the fact it rests on, and each fact links to its source.

Where the data comes from

• Risk ratings and expected losses: the FEMA National Risk Index, version 1.20 (December 2025), county layer. It covers 18 natural hazards. For each hazard and overall, FEMA publishes an Expected Annual Loss in dollars, a Risk Index that scales those losses by social vulnerability and community resilience, a score from 0 to 100 (the county's percentile rank among US counties) and a rating from Very Low to Very High.
• Disaster declarations: OpenFEMA Disaster Declarations Summaries, every federal major disaster, emergency and fire management declaration since 1953 that lists the county. We count natural hazards only, not biological (such as COVID-19) or other non-natural incidents.
• Flood insurance: OpenFEMA NFIP Residential Penetration Rates (policies in force and residential structures) and NFIP Redacted Claims. Claim counts and amounts paid per county are our tally of FEMA's claim records, in dollars of the year paid.
• Tornadoes: the NOAA Storm Prediction Center tornado database, 1950 to 2024. We count each tornado once for every county its record lists.
• How to prepare: steps from Ready.gov, FEMA's preparedness site, retold in plain words with a link to the page.

How to read FEMA's ratings

FEMA's ratings are relative. A county's rating compares it with all other US counties for the same hazard. FEMA uses k-means clustering (natural breaks) on the cube root of the values to set the five Risk and Expected Annual Loss ratings, and fixed quintiles of national percentiles for social vulnerability and community resilience. FEMA states that the index does not predict next year's losses and that a hazard can still cause damage where the rating is low. The data is meant for planning and is not a substitute for a local risk assessment.

Flood zones

Flood zones are drawn on FEMA flood maps (Flood Insurance Rate Maps) for specific properties. Our county pages do not tell you whether an address is in a flood zone. Use the FEMA Flood Map Service Center or ask your local floodplain manager.

How a page is made

1. We download the data sets and match each county across them by its FIPS code.
2. Code builds every table, rating scale and count straight from the data.
3. A writing step explains what the facts mean in plain English. Every number carries a reference to its fact.
4. A script checks every number and flags safety judgments, comparisons, forecasts and words that go beyond the facts. Then a separate review step checks each claim against the source before the page is published.

Credits

This product uses the Federal Emergency Management Agency's National Risk Index dataset API or downloadable datasets but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s). This product uses the FEMA OpenFEMA API, but is not endorsed by FEMA. NOAA Storm Prediction Center data and Ready.gov content are works of the US government.