Napa County— fire, flood & earthquake hazard information
Napa County is a county in the San Francisco Bay Area, covering about 752.0 square miles. This page summarizes what official government maps show for Napa County: CAL FIRE fire hazard severity zones, FEMA flood zones, state seismic hazard zones, dam inundation areas, airport noise contours, and air-quality indicators. Figures are the share of Napa County’s area that falls inside each mapped zone.
View Napa County on the interactive map → to check any specific address, free.
Wildfire hazard severity zones
Per CAL FIRE's Fire Hazard Severity Zone maps, 30% of Napa County is in a Very High fire hazard severity zone, 15% is in a High zone, 28% is in a Moderate zone. The remainder of its area is outside currently designated zones.
| Very High severity zone | 30% |
| High severity zone | 15% |
| Moderate severity zone | 28% |
FEMA flood zones
10% of Napa County lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO); less than 1% is in the 0.2% annual chance (500-year) area. Federally backed mortgages in a Special Flood Hazard Area generally require flood insurance.
| Special Flood Hazard Area (100-yr) | 10% |
| 0.2% annual chance (500-yr) | less than 1% |
Earthquake faults & seismic zones
The nearest mapped fault, the Atlas Peak-Foss Valley lineament zone, is about 1.6 mi (2.5 km) from the center of Napa County. 14 named fault traces in the USGS Quaternary fault database cross its boundary. 1% falls within an Alquist-Priolo earthquake fault zone, where new construction requires a fault study.
| Nearest mapped fault | Atlas Peak-Foss Valley lineament zone — 1.6 mi (2.5 km) |
| Named fault traces crossing boundary | 14 |
| Alquist-Priolo fault zone | 1% |
Dam inundation, aircraft noise & air quality
6% of Napa County lies within a state-reviewed dam-failure inundation area; annual average fine-particle (PM2.5) concentration across its census tracts is 7.5 μg/m³, and its composite pollution burden ranks around the 31th percentile statewide.
| Dam-failure inundation area | 6% |
| Annual PM2.5 (tract average) | 7.5 μg/m³ |
| Pollution burden percentile (statewide) | ~31 |
Frequently asked questions
- Is Napa County in a wildfire hazard severity zone?
- Per CAL FIRE's Fire Hazard Severity Zone maps, 30% of Napa County is in a Very High fire hazard severity zone, 15% is in a High zone, 28% is in a Moderate zone. The remainder of its area is outside currently designated zones.
- Is Napa County in a FEMA flood zone?
- 10% of Napa County lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO); less than 1% is in the 0.2% annual chance (500-year) area. Federally backed mortgages in a Special Flood Hazard Area generally require flood insurance.
- What earthquake faults and seismic zones affect Napa County?
- The nearest mapped fault, the Atlas Peak-Foss Valley lineament zone, is about 1.6 mi (2.5 km) from the center of Napa County. 14 named fault traces in the USGS Quaternary fault database cross its boundary. 1% falls within an Alquist-Priolo earthquake fault zone, where new construction requires a fault study.
- How do I check a specific address in Napa County?
- Use the free sitelume interactive map at https://sitelume.com — search any Napa County address to see which mapped zones it falls in, layer by layer.
Cities in Napa County
Sources: CAL FIRE Fire Hazard Severity Zones; FEMA National Flood Hazard Layer; USGS Quaternary Faults; CGS Seismic Hazard Zones & Alquist-Priolo zones; Cal OES dam inundation maps; county ALUC noise contours; CalEnviroScreen 4.0. Area shares are computed against each place’s Census TIGER boundary (last computed 2026-07-24). Boundaries and zone designations change; always verify with the issuing agency.