Data & methodology

Source

All risk scores and ratings on this site come directly from FEMA's National Risk Index (NRI), version 1.20.0, released December 2025. The NRI is a publicly available dataset published by FEMA at hazards.fema.gov/nri, covering expected annual losses, social vulnerability, and community resilience for natural hazards across the United States. SkyGround republishes the county-level table from that release without modification to the underlying figures.

What the scores mean

Each hazard (and the composite "Overall risk index") has a Score from 0–100 and a corresponding Rating. The score is a percentile: it reflects how a county's Risk Index value compares to every other county and county-equivalent in the country, not an absolute probability of a disaster occurring. The Risk Index value for each hazard is derived from three components:

Expected Annual Loss (EAL) — the modeled average loss in buildings, population, and agriculture each year from that hazard.
Social Vulnerability — community characteristics (from the CDC/ATSDR Social Vulnerability Index) that affect a community's ability to prepare for and recover from hazard events.
Community Resilience — a county's capacity to prepare for, adapt to, and recover from hazard events.

Ratings group the 0–100 score into five bands: Very Low, Relatively Low, Relatively Moderate, Relatively High, and Very High. Counties with a hazard that is not applicable in that area, or for which FEMA did not have enough data to compute a score, are shown as "Not Applicable" or "Insufficient Data" rather than a numeric score.

Hazards covered

Each county page shows all 18 hazard types in the NRI dataset: wildfire, inland flooding, coastal flooding, earthquake, heat wave, tornado, hurricane, hail, strong wind, winter weather, ice storm, cold wave, lightning, drought, landslide, avalanche, tsunami, and volcanic activity. Hazards that are not applicable for a given county (e.g., avalanche in Florida, coastal flooding in Kansas) are hidden by default and can be revealed with a toggle below the hazard table.

Coverage

SkyGround includes a page for every record in the NRI county table — 3,232 in total, covering all US counties and county-equivalents (including Louisiana parishes, Alaska boroughs and census areas, Virginia independent cities, Connecticut planning regions, and municipios of Puerto Rico and the US Virgin Islands).

Federal disaster declaration history

Alongside FEMA's modeled risk scores, each county page shows a summary of actual federal disaster declarations affecting that county, sourced from OpenFEMA's Disaster Declarations Summaries dataset. This is administrative data — it reflects which counties were included in a federal disaster declaration (and for what incident type), not a measure of modeled risk. A county can have a high modeled risk score with few declarations (if a disaster hasn't occurred recently) or a long declaration history with a lower current risk score (if conditions have changed). Statewide-only declarations (not tied to a specific county) are excluded from these counts. This dataset is refreshed periodically, independent of the NRI release cycle.

Recorded storm events

The hazard breakdown table shows a count of recorded events from NOAA's Storm Events Database for each applicable hazard, covering 2016–2026. This is observational data — actual recorded events — rather than a modeled score.

10 of the 18 hazards have county-level (CZ_TYPE = C) NOAA records: wildfire, inland flooding, tornado, drought, hail, hurricane, landslide, lightning, strong wind, and winter weather. Heat wave is sourced instead from NWS forecast-zone-level (CZ_TYPE = Z) records — NOAA overwhelmingly reports Heat and Excessive Heat events by forecast zone rather than county — assigned to counties via a zone-to-county crosswalk built from the NWS /points API. A single zone-wide event can therefore appear in the count for more than one county when a zone spans several counties (true for a small fraction of zones). Coastal flooding uses the same zone-level crosswalk internally but is not currently surfaced as an event count on its hazard page. Earthquake event counts come from the USGS ComCat catalog (M3.0+, 1996–2026), assigned to counties by nearest centroid within 75 km. The remaining 5 hazards (tsunami, ice storm, cold wave, avalanche, volcanic activity) show no recorded event count.

Each hazard row in the table also includes a trend sparkline showing event frequency by year (2016–2026). A wider bar means more events in that year relative to the same hazard's peak in this county.

ENSO / heat wave correlation

The heat wave leaderboard shows the current El Niño–Southern Oscillation (ENSO) phase and a comparison of NOAA-recorded heat-wave event counts across El Niño, La Niña, and Neutral years since 2016. This comes from NOAA CPC's Oceanic Niño Index (ONI), which NOAA updates monthly. Episodes are classified using NOAA's official rule (ONI at or beyond ±0.5°C for 5 or more consecutive overlapping 3-month seasons); a season meeting that threshold for fewer than 5 seasons is labeled "Emerging" rather than an official episode. Calendar years are bucketed by their mean ONI across the year's seasons. Because each phase bucket only covers 2–7 years in this window, the comparison is directional, not a statistically robust trend — other factors like long-term warming also affect event counts. This data is refreshed by re-running npm run fetch:enso, independent of the NRI release cycle.

Space weather data

SkyGround's space weather page shows live solar and geomagnetic conditions from NOAA SWPC. The CSV data download and JSON API also include each county's approximate geomagnetic latitude (dipole model, ~1° accuracy for CONUS) and the lowest planetary K-index at which aurora is typically visible — these are useful for research and tooling but are not currently displayed on individual county pages.

Identifiers

Each county has a stable 5-digit FIPS code (state + county), used throughout the CSV download and JSON API. The FIPS code can join SkyGround data with Census Bureau, EPA, USDA, and other federal datasets that use standard Census/FIPS geographic identifiers.

Limitations

Scores are relative rankings among US counties for the current NRI release, not predictions of whether or when a disaster will occur.
The underlying models are based on historical hazard occurrence and loss data and do not incorporate forward-looking climate projections.
County-level scores can mask significant variation within large or geographically diverse counties.
"Insufficient Data" and "Not Applicable" ratings reflect gaps or non-applicability in FEMA's source data, not a "no risk" determination.

Updates

FEMA periodically releases new versions of the National Risk Index. SkyGround is currently built from the December 2025 (v1.20.0) release and will be updated when a newer release becomes available.

Citing this data

When citing the underlying hazard data, please cite FEMA's National Risk Index directly (e.g., "FEMA National Risk Index, v1.20.0, December 2025, hazards.fema.gov/nri"). If referencing a specific county page on this site, you may additionally link to that page as the presentation source.