Weather & Climate in St. Helena, CA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
St. Helena enjoys a temperate climate with an average annual temperature of 61°F (16°C). Winters average 50°F in January while summers reach 72°F in July. Annual precipitation totals 34.0 inches. The city sits at an elevation of 222 feet.
Temperature
50°F Jan (10°C)
72°F Jul (22°C)
| Annual Average | 61.0°F |
| 13% above US avg | |
| January Average | 50°F (10°C) |
| July Average | 72°F (22°C) |
Geography
| Elevation | 222 ft (68 m) |
| Area | 5.0 sq mi (12.8 km²) |
| Population Density | 1,084/sq mi |
| Coordinates | 38.5128°N, 122.4681°W |
| Timezone | America/Los_Angeles |
| County | Napa County County |
| Nearest Airport | Sacramento International (SMF) 49 miles away |
Precipitation & Snow
Air Quality
Natural Hazard Risk
| Overall Risk | Relatively High |
| Risk Score | 95.3 / 100 |
| Social Vulnerability | 38.5 / 100 |
| Community Resilience | 76.0 / 100 |
Hazard Breakdown
| Tornado | Very Low |
| Earthquake | Relatively High |
| Wildfire | Relatively Moderate |
| Flood | Relatively High |
| Hail | Very Low |
| Strong Wind | Very Low |
| Heat Wave | Relatively Low |
| Winter Weather | Very Low |
| Lightning | Relatively Low |
| Drought | Very High |
| Cold Wave | No Rating |
| Landslide | Relatively High |
| Coastal Flood | Relatively Moderate |
| Tsunami | Very Low |
| Volcano | Very Low |
| Avalanche | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
4,255 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M6.0.
| Aug 24, 2014 | The 2014 South Napa, California Earthquake | M6.0 | 36 km | 11 km |
| Aug 10, 2016 | 20 km NNE of Upper Lake, California | M5.1 | 95 km | 14 km |
| Sep 3, 2000 | 5 km WSW of Yountville, California | M4.9 | 16 km | 9 km |
| Sep 4, 1995 | 13 km SW of Middletown, California | M4.8 | 31 km | 7 km |
| Apr 18, 2007 | 15 km N of Potter Valley, California | M4.8 | 119 km | 5 km |
| May 12, 2006 | 7 km W of Cobb, California | M4.7 | 45 km | 4 km |
| May 21, 1996 | 8 km ESE of East Foothills, California | M4.7 | 144 km | 8 km |
| Jan 2, 2025 | 4 km NW of Cobb, CA | M4.7 | 45 km | 1 km |
| Aug 18, 1999 | 0 km S of Bolinas, California | M4.6 | 70 km | 8 km |
| Jan 11, 2000 | 6 km N of Geyserville, California | M4.6 | 48 km | 6 km |
| Feb 18, 2004 | 4 km WNW of Cobb, California | M4.6 | 44 km | 3 km |
| Jan 12, 2014 | 8 km W of Cobb, California | M4.5 | 45 km | 2 km |
| Sep 25, 2012 | 3 km N of Talmage, California | M4.5 | 95 km | 11 km |
| Aug 3, 2006 | 5 km W of Glen Ellen, California | M4.5 | 20 km | 9 km |
| Jun 8, 2024 | 7 km NW of The Geysers, CA | M4.5 | 45 km | 4 km |
| Sep 19, 1992 | 7 km NW of Cobb, California | M4.5 | 48 km | 3 km |
| Apr 24, 2007 | 7 km WSW of Cobb, California | M4.5 | 42 km | 2 km |
| Jun 3, 2023 | 2km NW of The Geysers, CA | M4.5 | 41 km | 4 km |
| Mar 14, 2013 | 5 km W of Cobb, California | M4.4 | 43 km | 1 km |
| Mar 1, 2011 | 8 km W of Cobb, California | M4.4 | 45 km | 2 km |
Source: USGS Earthquake Catalog (M2.5+, 1990-2025). Sorted by magnitude.
Tornado History
51 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF2. Total: 1 injury.
| Date | Rating | Distance | Path | Fatalities |
| Feb 7, 1978 | EF2 | 91 km | 1.9 mi | 0 |
| Jun 1, 1958 | EF2 | 52 km | 15.0 mi | 0 |
| Oct 22, 2012 | EF1 | 95 km | 2.0 mi | 0 |
| Mar 18, 2011 | EF1 | 22 km | 0.1 mi | 0 |
| Jan 23, 2010 | EF1 | 91 km | 1.6 mi | 0 |
| Mar 20, 2005 | EF1 | 96 km | 3.0 mi | 0 |
| Jan 27, 2005 | EF1 | 58 km | 0.5 mi | 0 |
| Dec 5, 1998 | EF1 | 21 km | 1.5 mi | 0 |
| Dec 23, 1996 | EF1 | 50 km | 6.0 mi | 0 |
| Feb 22, 1996 | EF1 | 23 km | 1.0 mi | 0 |
| Dec 2, 1992 | EF1 | 31 km | 3.0 mi | 0 |
| Dec 2, 1992 | EF1 | 40 km | 7.5 mi | 0 |
| Dec 2, 1992 | EF1 | 34 km | 1.0 mi | 0 |
| Mar 22, 1983 | EF1 | 100 km | 2.0 mi | 0 |
| Feb 27, 1983 | EF1 | 21 km | 0.8 mi | 0 |
| Nov 10, 1964 | EF1 | 29 km | 1.0 mi | 0 |
| Feb 17, 1959 | EF1 | 68 km | 0.5 mi | 0 |
| Apr 1, 1958 | EF1 | 100 km | 0.2 mi | 0 |
| Sep 28, 2019 | EF0 | 63 km | 1.7 mi | 0 |
| Feb 2, 2019 | EF0 | 93 km | 0.3 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950-2024, US only).
Tsunami History
3 tsunamis recorded within 500 km. Highest wave on record: 4.5 m (15 ft).
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 1868 | N. CALIFORNIA | Eruption + Earthquake | 4.5 m | 30 | 96 km |
| 1856 | N. CALIFORNIA | Eruption + Earthquake | 0.6 m | - | 114 km |
| 1906 | N. CALIFORNIA | Eruption + Earthquake | 0.1 m | - | 90 km |
Source: NOAA/NCEI Historical Tsunami Database.
Nearby Volcanoes
1 volcano within 200 km. Closest: Clear Lake (57 km).
| Name | Type | Elevation | Last Eruption | Distance |
| Clear Lake | Volcanic field | 1,439 m (4,721 ft) | Unknown | 57 km |
Source: Smithsonian Institution Global Volcanism Program (GVP).
Wildfire History
20 wildfires (100+ acres) recorded within 100 km. Largest: RANCH (427,048 acres, 2018).
| Year | Name | Acres Burned | Distance |
| 2018 | RANCH | 427,048 | 88 km |
| 2020 | HENNESSEY | 314,241 | 20 km |
| 2015 | ROCKY | 96,125 | 44 km |
| 2018 | COUNTY | 92,450 | 33 km |
| 1996 | FORK | 83,209 | 80 km |
| 2019 | KINCADE | 77,780 | 32 km |
| 2015 | VALLEY | 77,507 | 33 km |
| 2020 | GLASS | 68,020 | 8 km |
| 2017 | NUNS | 56,883 | 19 km |
| 2020 | WALLBRIDGE | 55,194 | 48 km |
| 2017 | ATLAS | 51,664 | 26 km |
| 2018 | RIVER | 48,920 | 77 km |
| 2004 | RUMSEY | 39,335 | 32 km |
| 1999 | SIXTEEN | 37,162 | 35 km |
| 2017 | TUBBS | 36,981 | 19 km |
| 1988 | MILLER | 35,750 | 34 km |
| 2012 | MILL | 29,924 | 91 km |
| 2017 | 18,691 | 46 km | |
| 2012 | SIXTEEN COMPLEX | 18,191 | 57 km |
| 1987 | FOUTS | 16,892 | 97 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 50°F (10°C) | 6.5 in | |
| February | 52°F (11°C) | 6.7 in | |
| March | 55°F (13°C) | 5.0 in | |
| April | 59°F (15°C) | 2.0 in | |
| May | 64°F (18°C) | 1.3 in | |
| June | 70°F (21°C) | 0.4 in | |
| July | 72°F (22°C) | 0.0 in | Warmest, Driest |
| August | 72°F (22°C) | 0.0 in | |
| September | 70°F (21°C) | 0.1 in | |
| October | 64°F (18°C) | 1.7 in | |
| November | 55°F (13°C) | 3.2 in | |
| December | 49°F (9°C) | 7.2 in | Coldest, Wettest |
St. Helena has a seasonal temperature swing of 24°F / from 49°F in December to 72°F in July. Total annual precipitation is 34.0 inches, with December being the wettest month (7.2") and July the driest (0.0").