Floods
NWS · Updated Every 30 minutes · Source: NWS
About Floods
Flooding is the most common and costly natural disaster in the United States, occurring in every state and territory. Flash floods can develop within minutes of heavy rainfall while river flooding may build over days or weeks. Coastal storm surge, dam failures, and ice jams are additional flood triggers. Over 90% of federally declared disasters involve flooding.
Data Source
Alert polygons are fetched from the NWS API v3 (api.weather.gov), which serves all active CAP (Common Alerting Protocol) alerts in GeoJSON format. The API covers all NWS forecast offices and includes river flood statements, areal flood warnings, coastal flood advisories, and high surf advisories. FEMA flood zones are served as WMS tiles from ArcGIS Online.
| Detail | Value |
|---|---|
| Provider | NOAA National Weather Service |
| Update Frequency | Every 30 minutes |
| Coverage | United States (all 50 states and territories) |
| API / Data Feed | api.weather.gov/alerts |
What the Map Shows
Active NWS flood warnings (imminent or occurring flood event), flood watches (conditions favorable for flooding), and flood advisories (minor flooding expected). Each alert zone is color-coded by severity: red for warnings, orange for watches, yellow for advisories. FEMA National Flood Hazard Layer tiles show the broader Special Flood Hazard Areas (100-year floodplain).
View live Floods map →Explore Other Hazards
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