How fire-risk is classified across the US
The home page tells you what fire-risk classification applies to your area. The map page lets you overlay those classifications across the country. Two different ones are at work: a national category (sometimes called WUI) and a California-specific grade (sometimes called FRAP). This guide explains what each means, where it comes from, and why California has both.
Both classifications describe how exposed a place is to wildfire — they’re about geography and housing patterns, not about whether a fire is happening there right now. Active fires are a separate layer.
The national category
The national layer is the wildland-urban interface, or WUI. It’s a research dataset produced by a team at the University of Wisconsin–Madison, and it identifies places where buildings sit close enough to wildland that wildfires can reach them — neighborhoods edged against forest, scattered houses in brush country.
It’s built by overlaying two things: where people live (housing density) and where wildfires can spread (vegetation cover). Where the two coincide, the area is marked as a WUI zone. Where they don’t, it’s unmarked.
The national WUI map is binary — every square kilometer is either marked or not. It doesn’t grade severity. Two different WUI zones get the same label even if one is right next to a major fire-history corridor and the other is calm forest.
The dataset is rebuilt every few years from updated census and land-cover data. FireRiskHere uses the most recent published version.
The California grade
California has a separate, graded fire-hazard classification: Fire Hazard Severity Zones (FHSZ), with three levels — Moderate, High, and Very High. CAL FIRE, the state fire authority, maintains the maps as part of a program called FRAP, the Fire and Resource Assessment Program. FireRiskHere uses “FRAP” as the shorthand label for this classification on the map toggle, since that’s the name California uses publicly.
The California grade exists because the state built it. California uses these zones for building requirements, defensible-space rules (what homeowners must do to clear vegetation around houses), and insurance assessments — all of which need finer detail than a yes/no map can provide.
Two parts of the state have FHSZ — the State Responsibility Area (rural lands the state protects, where the zones were officially adopted, current map effective April 1, 2024) and the Local Responsibility Area (incorporated cities and some districts, where the recommended zones, last updated March 24, 2025, can be adopted by local governments for building codes).
A “Very High” zone is meaningfully different from a “Moderate” one. That difference is what makes the California grade more useful where it exists.
Why California has both
California is covered by the national WUI map (because that map covers the whole country) and by the California-specific grade (because the state built its own). The two overlap geographically — the coast and foothills are both WUI under the national dataset and graded under the California dataset.
On FireRiskHere, the California grade takes precedence where it exists. If you’re in a California Very High zone, you’ll see “Very High” — not the binary WUI mark — because the California grade is more specific.
Why other states see only the national one
There’s no federal equivalent to California’s graded classification. Some other states have local hazard maps in some places, but nothing covering an entire state with the same grading consistently. So for everywhere outside California, FireRiskHere shows the national WUI category and leaves it at that.
The map page’s classification toggle reflects this. Anywhere outside California, you can switch the overlay between “Off” and “WUI”. In California, you also see a “FRAP” option for the graded layer.
Full data sources and dates are on the methodology page.