St. Helena, CA— fire, flood & earthquake hazard information
St. Helena is a city in Napa County in the San Francisco Bay Area, covering about 5.0 square miles. This page summarizes what official government maps show for St. Helena: 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 St. Helena’s area that falls inside each mapped zone.
View St. Helena on the interactive map → to check any specific address, free.
Wildfire hazard severity zones
Per CAL FIRE's Fire Hazard Severity Zone maps, 3% of St. Helena is in a Very High fire hazard severity zone, less than 1% is in a High zone, less than 1% is in a Moderate zone. The remainder of its area is outside currently designated zones.
| Very High severity zone | 3% |
| High severity zone | less than 1% |
| Moderate severity zone | less than 1% |
FEMA flood zones
8% of St. Helena lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO); 4% 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) | 8% |
| 0.2% annual chance (500-yr) | 4% |
Earthquake faults & seismic zones
The nearest mapped fault, the West Napa fault, is about 1.1 mi (1.8 km) from the center of St. Helena. 1 named fault trace in the USGS Quaternary fault database cross its boundary.
| Nearest mapped fault | West Napa fault — 1.1 mi (1.8 km) |
| Named fault traces crossing boundary | 1 |
Dam inundation, aircraft noise & air quality
15% of St. Helena lies within a state-reviewed dam-failure inundation area; annual average fine-particle (PM2.5) concentration across its census tracts is 7.9 μg/m³, and its composite pollution burden ranks around the 37th percentile statewide.
| Dam-failure inundation area | 15% |
| Annual PM2.5 (tract average) | 7.9 μg/m³ |
| Pollution burden percentile (statewide) | ~37 |
Frequently asked questions
- Is St. Helena in a wildfire hazard severity zone?
- Per CAL FIRE's Fire Hazard Severity Zone maps, 3% of St. Helena is in a Very High fire hazard severity zone, less than 1% is in a High zone, less than 1% is in a Moderate zone. The remainder of its area is outside currently designated zones.
- Is St. Helena in a FEMA flood zone?
- 8% of St. Helena lies within a FEMA Special Flood Hazard Area (1% annual chance, zones A/AE/AH/AO); 4% 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 St. Helena?
- The nearest mapped fault, the West Napa fault, is about 1.1 mi (1.8 km) from the center of St. Helena. 1 named fault trace in the USGS Quaternary fault database cross its boundary.
- How do I check a specific address in St. Helena?
- Use the free sitelume interactive map at https://sitelume.com — search any St. Helena address to see which mapped zones it falls in, layer by layer.
Nearby 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.