How to read the National Risk Index
A county page of this site shows the National Risk Index of FEMA for the county. The site shows the table of the December 2025 release (version 1.20) and does not change it. This guide follows the FAQ and the data glossary of FEMA for that release.
The National Risk Index dataset leverages available source data for natural hazard and community risk factors to develop a baseline relative risk measurement for each United States county and Census tract.
Parts of the index
The Risk Index has three parts: Expected Annual Loss, Social Vulnerability and Community Resilience. The data glossary of FEMA defines each part. The glossary page of this site quotes the definitions.
FEMA says that the Social Vulnerability data comes from the Community Resilience Estimates of the Census Bureau. The Community Resilience data comes from the University of South Carolina. A county page shows FEMA's labels for them.
Scores and ratings
A score is a percentile from 0 to 100. A rating is a name from Very Low to Very High.
The rating is a qualitative categorization that describes the community in comparison to all other communities at the same level, ranging from “Very Low” to “Very High.”
A rating of a county does not give the chance of an event in the county. It places the county among all counties.
What the ratings do not show
Levees, dams, or other flood control structures are factored into the coastal or inland flooding hazards of the National Risk Index only if the features are incorporated into the source datasets.
With these factors, even if a community experiences a large-scale event, its risk may be relatively low overall if it has a highly resilient population, a relatively low overall frequency of hazards, etc.
FEMA states the purpose of the data.
The National Risk Index data are meant for planning purposes only.
Connecticut
The December 2025 release has planning regions for Connecticut. This site uses the eight Connecticut counties, so a Connecticut county page has no Risk Index.
Date of the last check against the agency pages: