Wildfire Risk in the US: How FEMA Scores It and How to Prepare

Wildfire has gone from a regional concern to one of the defining American disaster risks in a single generation. The deadliest US fire in a century (Camp Fire, Paradise, CA, 2018), the costliest urban firestorms (Los Angeles, January 2025), and the Maui fire of 2023 all share one anatomy: wind-driven fire reaching neighborhoods built into flammable landscapes. In the National Risk Index, wildfire (hazard code WFIR) carries roughly $3.9 billion in national expected annual loss — with measurable risk in all 3,143 counties, but extreme concentration in a handful of them.

What counts as wildfire risk

The NRI’s wildfire hazard covers uncontrolled fires in vegetation — forest, brush, and grass — including those that transition into communities. The decisive concept is the wildland-urban interface (WUI): the zone where homes intermingle with burnable vegetation. Fire behavior in the WUI is dominated by embers, which can travel a mile or more ahead of a fire front and ignite homes through vents, gutters full of needles, and wooden fences attached to the house. Most homes lost in wildfires are ignited by embers, not by a wall of flame.

Fire needs fuel, dryness, and wind. That is why the worst events cluster in wind seasons — Santa Ana and Diablo winds in California, chinook winds along the Front Range — and in drought years, when fuels reach single-digit moisture.

How the NRI measures it

FEMA builds each county’s wildfire Expected Annual Loss from exposure (building value, population, and agriculture in burnable areas, using US Forest Service wildfire hazard potential data), annualized fire frequency, and the historic loss ratio of fire events. The result is scored 0–100 against all other counties.

Because exposure drives the math, the ranking rewards places where expensive housing meets flammable terrain — not necessarily where the most acres burn. Millions of acres burn in sparsely populated rangeland every year with modest dollar losses.

Where the risk concentrates

Southern California owns the top of the national ranking. Riverside County and San Diego County lead with wildfire scores of 100 and expected annual losses around $347M and $430M respectively, followed by Los Angeles and San Bernardino counties (~$155M and $146M). The pattern extends through the Sierra foothills, and high ratings continue through Nevada (Elko County is a top-five county nationally), Arizona, Colorado’s Front Range, Oregon, Washington, and the Texas Hill Country. Fast-growing WUI development in the Mountain West is pushing risk up steadily, and events like the 2021 Marshall Fire in suburban Boulder County, Colorado — a December grass fire that destroyed over 1,000 homes — show the risk is no longer confined to forested mountains.

How to read your county’s score

A Very High county score means substantial value sits where fire can reach it — but wildfire is the most parcel-specific hazard in the index. Within the same county, a home in a stucco subdivision surrounded by irrigated lawns and a home on a brushy canyon rim face utterly different odds. Use the county score as a prompt to check your specific parcel: state fire-hazard severity maps (California’s CAL FIRE maps are the model), and whether your insurer is repricing or non-renewing in your area — insurance availability has become a leading indicator of fire risk.

What actually reduces the risk

Research from IBHS and post-fire damage surveys is unusually clear on what saves homes:

• Harden against embers first. Ember-resistant vents (1/8” metal mesh), clean gutters, and no combustible mulch or vegetation within 5 feet of the structure (Zone 0) matter more than anything else. California now mandates ember-resistant Zone 0 for new WUI construction.
• Roof and siding class. A Class A roof (asphalt shingle, metal, tile with bird-stops) is the single most important structural feature. Wood-shake roofs are catastrophic.
• Defensible space, 0–100 feet. Thin vegetation, limb trees, break up fuel continuity. A wooden fence touching the house is a fuse — replace the last 5 feet with metal.
• Plan to leave early. Fatalities cluster in late evacuations. Know two ways out, sign up for county alerts, and treat Red Flag Warning days as pre-positioning days.
• Insurance before the smoke. Binding moratoriums freeze new coverage once a fire ignites nearby. Review dwelling limits annually; rebuild costs after big fires routinely exceed pre-fire estimates.

Sources

• US Forest Service Wildfire Risk to Communities — parcel-level risk maps
• FEMA NRI wildfire methodology
• IBHS Wildfire Prepared Home — the research-backed hardening standard
• Ready.gov wildfire preparedness