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Weather & Climate in Rio Oso, CA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Rio Oso enjoys a temperate climate with an average annual temperature of 61°F (16°C). Winters average 47°F in January while summers reach 76°F in July. The area gets 330 sunny days per year, well above the U.S. average of 205 / making it one of the sunnier locations in the country. Annual precipitation totals 18.0 inches (drier than the 38-inch national average). Air quality is rated Good with a median AQI of 48. The city sits at an elevation of 44 feet.
Temperature
47°F Jan (8°C)
76°F Jul (25°C)
| Annual Average | 61.2°F |
| 13% above US avg | |
| January Average | 47°F (8°C) |
| July Average | 76°F (25°C) |
| Sunny Days | 330 days/yr |
Geography
| Elevation | 44 ft (13 m) |
| Area | 6.5 sq mi (16.9 km²) |
| Population Density | 65/sq mi |
| Coordinates | 38.9518°N, 121.5310°W |
| Timezone | America/Los_Angeles |
| County | Yolo County County |
| Nearest Airport | Sacramento International (SMF) 18 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 48.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Moderate |
| Risk Score | 91.4 / 100 |
| Social Vulnerability | 24.2 / 100 |
| Community Resilience | 69.4 / 100 |
Hazard Breakdown
| Tornado | Very Low |
| Earthquake | Relatively Moderate |
| Wildfire | Relatively Low |
| Flood | Relatively Moderate |
| 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 Low |
| Volcano | Very Low |
| Avalanche | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
4,632 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 | 106 km | 11 km |
| May 24, 2013 | 2 km NNE of Canyondam, California | M5.7 | 144 km | 8 km |
| May 11, 2023 | Lake Almanor Earthquake | M5.5 | 144 km | 6 km |
| Aug 10, 2001 | 3 km N of Blairsden, California | M5.2 | 124 km | 5 km |
| May 12, 2023 | 4km NW of Canyondam, CA | M5.2 | 143 km | 6 km |
| Aug 10, 2016 | 20 km NNE of Upper Lake, California | M5.1 | 117 km | 14 km |
| Sep 3, 2000 | 5 km WSW of Yountville, California | M4.9 | 100 km | 9 km |
| May 24, 2013 | 1km NNW of Canyondam, CA | M4.9 | 142 km | 4 km |
| Oct 30, 1998 | 4 km N of Tahoe Vista, California | M4.8 | 133 km | 1 km |
| Sep 4, 1995 | 13 km SW of Middletown, California | M4.8 | 109 km | 7 km |
| Apr 18, 2007 | 15 km N of Potter Valley, California | M4.8 | 147 km | 5 km |
| Jun 26, 2005 | 8 km NNW of Tahoe Vista, California | M4.8 | 130 km | -2 km |
| May 12, 2006 | 7 km W of Cobb, California | M4.7 | 112 km | 4 km |
| Jan 2, 2025 | 4 km NW of Cobb, CA | M4.7 | 107 km | 1 km |
| May 7, 2021 | 19km NW of Truckee, CA | M4.7 | 119 km | 10 km |
| Jan 11, 2000 | 6 km N of Geyserville, California | M4.6 | 121 km | 6 km |
| Feb 18, 2004 | 4 km WNW of Cobb, California | M4.6 | 108 km | 3 km |
| Jan 12, 2014 | 8 km W of Cobb, California | M4.5 | 112 km | 2 km |
| Sep 25, 2012 | 3 km N of Talmage, California | M4.5 | 143 km | 11 km |
| Aug 3, 2006 | 5 km W of Glen Ellen, California | M4.5 | 113 km | 9 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
79 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF2. Total: 7 injuries.
| Date | Rating | Distance | Path | Fatalities |
| May 25, 2011 | EF2 | 72 km | 0.2 mi | 0 |
| Feb 10, 1994 | EF2 | 63 km | 0.3 mi | 0 |
| Feb 7, 1978 | EF2 | 29 km | 1.9 mi | 0 |
| Dec 19, 2023 | EF1 | 98 km | 0.4 mi | 0 |
| Dec 24, 2015 | EF1 | 45 km | 6.2 mi | 0 |
| Mar 26, 2014 | EF1 | 85 km | 1.0 mi | 0 |
| Mar 26, 2014 | EF1 | 88 km | 0.6 mi | 0 |
| Mar 26, 2014 | EF1 | 86 km | 0.7 mi | 0 |
| Oct 22, 2012 | EF1 | 15 km | 2.0 mi | 0 |
| Oct 22, 2012 | EF1 | 14 km | 0.3 mi | 0 |
| Oct 22, 2012 | EF1 | 39 km | 4.0 mi | 0 |
| May 25, 2011 | EF1 | 86 km | 26.4 mi | 0 |
| May 25, 2011 | EF1 | 92 km | 21.7 mi | 0 |
| Jan 8, 2005 | EF1 | 56 km | 0.1 mi | 0 |
| Apr 17, 1993 | EF1 | 82 km | 0.5 mi | 0 |
| Jan 7, 1993 | EF1 | 55 km | 0.1 mi | 0 |
| Dec 17, 1992 | EF1 | 63 km | 1.0 mi | 0 |
| Dec 17, 1992 | EF1 | 43 km | 5.0 mi | 0 |
| Apr 19, 1988 | EF1 | 93 km | 0.2 mi | 0 |
| Apr 19, 1988 | EF1 | 44 km | 1.0 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Tsunami History
1 tsunami 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 | 148 km |
Source: NOAA/NCEI Historical Tsunami Database.
Nearby Volcanoes
2 volcanoes within 200 km. Closest: Clear Lake (107 km).
| Name | Type | Elevation | Last Eruption | Distance |
| Clear Lake | Volcanic field | 1,439 m (4,721 ft) | Unknown | 107 km |
| Lassen Volcanic Center | Stratovolcano | 3,187 m (10,456 ft) | 1917 | 171 km |
Source: Smithsonian Institution Global Volcanism Program (GVP).
Wildfire History
20 wildfires (100+ acres) recorded within 100 km. Largest: NORTH COMPLEX (316,556 acres, 2020).
| Year | Name | Acres Burned | Distance |
| 2020 | NORTH COMPLEX | 316,556 | 93 km |
| 2020 | HENNESSEY | 314,241 | 75 km |
| 2018 | CAMP | 153,687 | 89 km |
| 2014 | KING | 99,070 | 86 km |
| 2015 | ROCKY | 96,125 | 80 km |
| 2018 | COUNTY | 92,450 | 62 km |
| 2022 | MOSQUITO | 77,858 | 73 km |
| 2015 | VALLEY | 77,507 | 95 km |
| 2020 | GLASS | 68,020 | 99 km |
| 2017 | ATLAS | 51,664 | 90 km |
| 2004 | RUMSEY | 39,335 | 68 km |
| 1999 | SIXTEEN | 37,162 | 71 km |
| 1988 | 49R | 36,673 | 43 km |
| 1988 | MILLER | 35,750 | 76 km |
| 2013 | AMERICAN | 27,938 | 84 km |
| 2008 | CANYON COMPLEX (SCOTCH) | 26,418 | 91 km |
| 2008 | HUMBOLDT | 23,769 | 85 km |
| 1992 | CLEVELAND | 21,835 | 96 km |
| 2008 | AMERICAN RIVER COMPLEX (GOVERNMENT) | 20,709 | 86 km |
| 2012 | SIXTEEN COMPLEX | 18,191 | 67 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 47°F (8°C) | 3.7 in | Wettest |
| February | 51°F (11°C) | 3.0 in | |
| March | 55°F (13°C) | 2.8 in | |
| April | 60°F (16°C) | 1.3 in | |
| May | 68°F (20°C) | 0.4 in | |
| June | 74°F (23°C) | 0.2 in | |
| July | 76°F (25°C) | 0.1 in | Warmest, Driest |
| August | 75°F (24°C) | 0.1 in | |
| September | 72°F (22°C) | 0.4 in | |
| October | 64°F (18°C) | 1.3 in | |
| November | 53°F (12°C) | 3.1 in | |
| December | 46°F (8°C) | 2.9 in | Coldest |
Rio Oso has a seasonal temperature swing of 30°F / from 46°F in December to 76°F in July. Total annual precipitation is 19.3 inches, with January being the wettest month (3.7") and July the driest (0.1").