Sonoma County— fire, flood & earthquake hazard information
Sonoma County is a county in the San Francisco Bay Area, covering about 1575.3 square miles. This page summarizes what official government maps show for Sonoma 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 Sonoma County’s area that falls inside each mapped zone.
View Sonoma County on the interactive map → to check any specific address, free.
Wildfire hazard severity zones
Per CAL FIRE's Fire Hazard Severity Zone maps, 13% of Sonoma County is in a Very High fire hazard severity zone, 35% is in a High zone, 21% is in a Moderate zone. The remainder of its area is outside currently designated zones.
| Very High severity zone | 13% |
| High severity zone | 35% |
| Moderate severity zone | 21% |
FEMA flood zones
5% of Sonoma County lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO); less than 1% is in a coastal high hazard zone (V/VE); 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) | 5% |
| Coastal high hazard (V/VE) | less than 1% |
| 0.2% annual chance (500-yr) | less than 1% |
Earthquake faults & seismic zones
The nearest mapped fault, the Mt. Jackson fault zone, is about 1.4 mi (2.3 km) from the center of Sonoma County. 23 named fault traces in the USGS Quaternary fault database cross its boundary. less than 1% of its area is in a state-designated liquefaction zone of required investigation. less than 1% is in an earthquake-induced landslide zone. 2% falls within an Alquist-Priolo earthquake fault zone, where new construction requires a fault study.
| Nearest mapped fault | Mt. Jackson fault zone — 1.4 mi (2.3 km) |
| Named fault traces crossing boundary | 23 |
| Liquefaction zone | less than 1% |
| Earthquake-induced landslide zone | less than 1% |
| Alquist-Priolo fault zone | 2% |
Dam inundation, aircraft noise & air quality
1% of Sonoma County lies within a state-reviewed dam-failure inundation area; annual average fine-particle (PM2.5) concentration across its census tracts is 6.3 μg/m³, and its composite pollution burden ranks around the 28th percentile statewide.
| Dam-failure inundation area | 1% |
| Annual PM2.5 (tract average) | 6.3 μg/m³ |
| Pollution burden percentile (statewide) | ~28 |
Frequently asked questions
- Is Sonoma County in a wildfire hazard severity zone?
- Per CAL FIRE's Fire Hazard Severity Zone maps, 13% of Sonoma County is in a Very High fire hazard severity zone, 35% is in a High zone, 21% is in a Moderate zone. The remainder of its area is outside currently designated zones.
- Is Sonoma County in a FEMA flood zone?
- 5% of Sonoma County lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO); less than 1% is in a coastal high hazard zone (V/VE); 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 Sonoma County?
- The nearest mapped fault, the Mt. Jackson fault zone, is about 1.4 mi (2.3 km) from the center of Sonoma County. 23 named fault traces in the USGS Quaternary fault database cross its boundary. less than 1% of its area is in a state-designated liquefaction zone of required investigation. less than 1% is in an earthquake-induced landslide zone. 2% falls within an Alquist-Priolo earthquake fault zone, where new construction requires a fault study.
- How do I check a specific address in Sonoma County?
- Use the free sitelume interactive map at https://sitelume.com — search any Sonoma County address to see which mapped zones it falls in, layer by layer.
Cities in Sonoma 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.