How we check
Sources & methodology
Hazard findings come from the public datasets below, read from the agency’s own service when you check an address (we reuse a result for up to 24 hours). A failed or out-of-coverage lookup is always shown as such, never as low risk. We link a source for every figure we can. If one is missing, tell us.
Datasets we check
| Dataset | What it tells us | Vintage / update cadence | Resolution | Known limits |
|---|---|---|---|---|
| U.S. Census Bureau geocoder | Turns the address you type into a matched address, coordinates, county and state, so every other check can run against a real point. | Continuously maintained address data (TIGER/Line-based); not a dated snapshot. | Point | Matches to the closest known address. Brand-new addresses, rural routes and typos may not match, or may match to the wrong spot. |
| FEMA National Flood Hazard Layer | Your FEMA flood zone (for example X, AE or VE) and whether you’re inside a Special Flood Hazard Area. | Updated continuously as FEMA processes map changes; there’s no single revision date that covers every zone. | Point | A point-in-polygon lookup at the geocoded address, not a survey of your building. FEMA’s own map site is the official answer for your exact parcel. |
| CAL FIRE FRAP historic fire perimeters | In California, fires of 100+ acres that have burned near you going back decades. | Updated as CAL FIRE closes out and maps each fire season. | Area | California only. We only count wildfires from the last 5 years within about a mile; prescribed burns are excluded. Distance is measured to the middle of the burn area, not its nearest edge. |
| NIFC WFIGS interagency fire perimeters | Wildfires of 100+ acres that have burned near you in recent years, including this year’s, in all 13 states this site covers. | Refreshed continuously through fire season, often within hours of a fire being mapped. | Area | Wildfires only; prescribed burns are excluded. We only count fires from the last 5 years within about a mile, measured to the middle of the burn area. A fire that started very recently may not be mapped yet. |
| LA County Public Works post-fire debris-flow hazard areas | Whether you’re within about 500 meters (about a third of a mile) of a post-fire debris-flow hazard area mapped by LA County Public Works below a recent burn scar. | Updated as LA County Public Works maps new fires. | Area | Our check uses these maps for spots in LA County only. Elsewhere in the 13 states this site covers, it uses USGS assessments (next row). For fires neither has mapped, it shows “Not covered”, not a low result. |
| USGS post-fire debris-flow hazard assessments | Outside LA County, whether you’re within about 500 meters (about a third of a mile) of a basin or channel below a recent burn that USGS rates for post-fire debris-flow hazard, from low to high. | USGS assesses each fire once, usually two to four weeks after it starts, and adds new fires as it goes. We show the assessment date. | Area | USGS assesses recent large fires on steep ground, mostly in the West. As of September 2026 it had assessed none in Texas, Louisiana, Mississippi, Alabama, Florida, Georgia or South Carolina. A spot outside an assessed fire’s area, or near a newer fire the assessment came before, shows “Not covered”, not a low result. |
| California Geological Survey Map Sheet 58 | An area-level susceptibility class for deep-seated landslides, from 0 (lowest) up to X (highest). | Map Sheet 58, published 2011. | Area | A statewide raster, not a site assessment. The High / Moderate / Lower labels are our own split of CGS’s classes, not CGS’s: classes VIII–X show as High, V–VII as Moderate, and anything lower as Lower mapped risk. A very recently active slide may read differently on this map than what you’d observe on the ground. |
| USGS U.S. Landslide Inventory and Susceptibility (county table) | In the 12 states besides California that this site covers, the share of your county’s land that USGS maps as susceptible to landslides, and how many landslides its national inventory lists there. | A national data release published in August 2024. We use a fixed copy of its county table. | Area | A county-wide figure, never a rating for your address: a mostly flat county can still have steep slopes, and the reverse. The inventory counts only landslides someone mapped, so a low count doesn’t mean stable ground. California uses the state’s Map Sheet 58 instead. |
| California Geological Survey tsunami hazard areas | Whether your point falls inside an official tsunami evacuation/hazard area. | Per-county planning maps; CGS doesn’t publish one shared revision date across counties. | Point | Only coastal counties are mapped. Always follow official evacuation orders over any map, including this one. |
| National Weather Service active alerts | Live NWS warnings, watches and advisories covering your point right now. | Real time. Never cached, so it’s always current as of the moment you check. | Area | Alerts are issued for a forecast zone or county, not a single address. |
| US EPA community water system service area boundaries | In the 12 states besides California that this site covers, which community water system may serve your address, so you know who would issue a boil-water notice there. | A national map EPA updates from time to time. We show its last-updated date (May 2026 when we checked it in September 2026). | Point | Some boundaries are EPA’s own estimates, not the water system’s map: then we say the spot “may be served by” it and link your state’s drinking-water program. Boundaries can overlap. Your water bill is the sure answer, and boil-water notices come from your water system and state, not from this map. California uses the State Water Board’s map instead. |
| Electric Retail Service Territories (HIFLD) | In the 12 states besides California that this site covers, which electric utilities may serve your address, so we can link their official outage maps. | Territory records dated August 2023, read from a copy hosted on ArcGIS Online. | Point | Territories overlap and are simplified, so we list the utilities that may serve the spot, never “your utility”: your bill is the sure answer. We link only outage pages we opened and checked in September 2026. The copy we read isn’t hosted by HIFLD itself, and we couldn’t confirm it against the original. |
| FEMA OpenFEMA, Disaster Declarations Summaries | Whether a recent federal disaster declaration covers your county, and whether FEMA help for households is open to apply for. | Updated by FEMA as declarations are made and changed. We reuse a result for up to 6 hours. | Area | County-wide, not your address. We read FEMA’s program flags (help for households, public assistance, hazard mitigation) and the last day to apply; when FEMA hasn’t set that day yet, help counts as open for 120 days after the declaration. Tribal-area declarations aren’t tied to a county, so we list them for the whole state. “No open assistance” means none in FEMA’s list; DisasterAssistance.gov checks your own address. |
| NOAA Climate Prediction Center ENSO status | The current El Niño/La Niña status (the ENSO Alert level) and the Oceanic Niño Index, which is what makes a given winter an “El Niño year” or not. | Updated monthly, roughly mid-month; the source page states the exact date of its next update. | Regional | A Pacific-basin climate outlook, not a California-specific or local forecast. |
How to read a result
Every hazard finding on this site uses one of these results. None of them means “safe.”
- High
- The map places you inside its highest hazard class for this check — for example, a FEMA Special Flood Hazard Area. For landslides, High is our label for CGS susceptibility classes VIII–X.
- Moderate
- Near, but not inside, the highest hazard class — for example, a 0.2%-annual-chance flood zone. For landslides, Moderate is our label for CGS susceptibility classes V–VII.
- Lower mapped risk
- The map doesn’t place you in a hazard zone for this check. We say “lower mapped risk,” never “safe” — official maps miss some real risk, and conditions change.
- Not mapped
- The agency has no specific hazard rating for this exact point — for example, an area FEMA hasn’t digitized, or FEMA’s Zone D, which is officially “possible but undetermined flood hazard.” It isn’t a low result; the map is simply silent here.
- Undetermined
- Some datasets return an explicit “not yet determined” answer for a spot rather than a hazard level, most commonly FEMA’s Zone D. We treat that the same as “Not mapped” rather than guess at a level.
- Couldn’t check
- The government service didn’t respond in time, even after one retry. We show this instead of guessing, with a link to the official map so you can look it up by hand.
- Not covered
- This dataset doesn’t map your area at all — the tsunami map only covers coastal counties, for instance, and several checks only cover California. That’s a different thing from a clean result, so we never show it as low risk.
What we don’t check
To keep the site’s claims bounded to what these datasets actually support, we don’t check:
- Earthquake or seismic hazard: fault zones, liquefaction or shaking intensity.
- Wildfire behavior modeling — we show historical and current-year burn perimeters and post-fire debris-flow zones, not a prediction of where a future fire might spread.
- Wind, hail, extreme heat, drought, or air quality and smoke.
- Shallow landslides, rockfall, or slope stability outside CGS’s statewide deep-seated landslide map.
- A parcel-level or engineering assessment of your specific building. Every check here is a point-in-polygon or area-level lookup against a public map, not a site inspection.
- Most hazards outside the 13 states this site covers (California, Arizona, New Mexico, Nevada, Utah, Texas, Louisiana, Mississippi, Alabama, Florida, Georgia, South Carolina and North Carolina). Anywhere in the U.S., the address check still runs the Census geocoder, FEMA’s flood map and NWS alerts; the other checks show “Not covered” there. The landslide and tsunami checks cover California only.