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Weather & Climate in Thornton, CA

Temperature, precipitation, air quality, natural hazards, and monthly weather data.

Thornton enjoys a temperate climate with an average annual temperature of 62°F (17°C). Winters average 48°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 18.4 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 10 feet.

Temperature

48°F Jan (9°C) 76°F Jul (24°C)
Annual Average62.2°F
15% above US avg
January Average48°F (9°C)
July Average76°F (24°C)
Sunny Days330 days/yr

Geography

Elevation10 ft (3 m)
Area2.2 sq mi (5.6 km²)
Population Density383/sq mi
Coordinates38.2297°N, 121.4261°W
TimezoneAmerica/Los_Angeles
CountySacramento County County
Nearest AirportSacramento International (SMF)
33 miles away

Precipitation & Snow

Annual Rainfall 18.4"
52% below US avg
Snowfall 0.0"
Wettest Month (Jan) 3.62"
Driest Month (Jul) 0.04"

Air Quality

AQI Median48.0
RatingGood

Natural Hazard Risk

Overall RiskRelatively High
Risk Score98.1 / 100
Social Vulnerability37.4 / 100
Community Resilience57.0 / 100

Hazard Breakdown

Tornado Relatively Moderate
Earthquake Relatively High
Wildfire Relatively Moderate
Flood Relatively High
Hail Relatively Low
Strong Wind Very Low
Heat Wave Relatively Moderate
Winter Weather Very Low
Lightning Relatively Moderate
Drought Relatively High
Cold Wave No Rating
Landslide Relatively Low
Coastal Flood No Rating
Volcano Very Low
Source: FEMA National Risk Index v1.20 (Dec 2025)

Earthquake History

4,397 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 77 km 11 km
Apr 18, 1990 5 km NNW of Aromas, California M5.4 146 km 5 km
Apr 18, 1990 4 km E of Interlaken, California M5.1 143 km 7 km
Jan 16, 1993 9 km E of Gilroy, California M4.9 135 km 7 km
Apr 18, 1990 4 km NNW of Aromas, California M4.9 146 km 6 km
Sep 3, 2000 5 km WSW of Yountville, California M4.9 88 km 9 km
May 14, 2002 5 km SSW of Gilroy, California M4.9 141 km 7 km
Sep 4, 1995 13 km SW of Middletown, California M4.8 125 km 7 km
May 12, 2006 7 km W of Cobb, California M4.7 137 km 4 km
Apr 18, 1990 4 km N of Aromas, California M4.7 146 km 4 km
May 21, 1996 8 km ESE of East Foothills, California M4.7 100 km 8 km
Aug 11, 1993 14 km ESE of Alum Rock, California M4.7 104 km 9 km
Jan 2, 2025 4 km NW of Cobb, CA M4.7 134 km 1 km
Mar 24, 1991 1 km NNE of Interlaken, California M4.6 143 km 15 km
Aug 18, 1999 0 km S of Bolinas, California M4.6 116 km 8 km
Jan 11, 2000 6 km N of Geyserville, California M4.6 143 km 6 km
Feb 18, 2004 4 km WNW of Cobb, California M4.6 135 km 3 km
Sep 19, 2023 15 km SW of Westley, CA M4.5 89 km 4 km
Jan 12, 2014 8 km W of Cobb, California M4.5 137 km 2 km
Aug 3, 2006 5 km W of Glen Ellen, California M4.5 103 km 9 km
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.

Tornado History

78 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF2. Total: 2 injuries.

Date Rating Distance Path Fatalities
Feb 7, 1978 EF2 52 km 1.9 mi 0
Apr 27, 1953 EF2 75 km 0.1 mi 0
Mar 11, 2023 EF1 85 km 0.8 mi 0
Jan 10, 2023 EF1 61 km 0.4 mi 0
Dec 24, 2015 EF1 59 km 6.2 mi 0
Nov 15, 2015 EF1 95 km 3.0 mi 0
Oct 22, 2012 EF1 94 km 2.0 mi 0
Oct 22, 2012 EF1 95 km 0.3 mi 0
Oct 22, 2012 EF1 95 km 4.0 mi 0
Jan 23, 2010 EF1 46 km 1.6 mi 0
Apr 14, 2006 EF1 75 km 0.5 mi 0
Dec 12, 1996 EF1 72 km 0.6 mi 0
Apr 19, 1988 EF1 25 km 0.2 mi 0
Apr 19, 1988 EF1 55 km 1.0 mi 0
Mar 22, 1983 EF1 55 km 2.0 mi 0
Jan 14, 1980 EF1 92 km 0.3 mi 0
Mar 4, 1978 EF1 85 km 2.5 mi 0
Mar 1, 1978 EF1 76 km 1.5 mi 0
May 31, 1967 EF1 31 km 0.1 mi 0
Jan 14, 2023 EF0 27 km 0.3 mi 0
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).

Tsunami History

5 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 83 km
1989 N. CALIFORNIA Earthquake 1.0 m 62 139 km
1856 N. CALIFORNIA Eruption + Earthquake 0.6 m — 112 km
1906 N. CALIFORNIA Eruption + Earthquake 0.1 m — 111 km
1865 N. CALIFORNIA Eruption + Earthquake — — 122 km
Source: NOAA/NCEI Historical Tsunami Database.

Nearby Volcanoes

1 volcano within 200 km. Closest: Clear Lake (143 km).

Name Type Elevation Last Eruption Distance
Clear Lake Volcanic field 1,439 m (4,721 ft) Unknown 143 km
Source: Smithsonian Institution Global Volcanism Program (GVP).

Wildfire History

20 wildfires (100+ acres) recorded within 100 km. Largest: SCU LIGHTNING COMPLEX (405,787 acres, 2020).

Year Name Acres Burned Distance
2020 SCU LIGHTNING COMPLEX 405,787 82 km
2020 HENNESSEY 314,241 87 km
2018 COUNTY 92,450 81 km
2015 BUTTE 72,894 73 km
2017 NUNS 56,883 95 km
2017 ATLAS 51,664 72 km
2004 RUMSEY 39,335 94 km
2006 CANYON 36,851 97 km
1988 MILLER 35,750 62 km
1992 GULCH 18,019 83 km
2024 CORRAL 16,138 66 km
2001 DARBY 14,734 98 km
2006 ZAM ASSIST 14,404 72 km
2018 WAVERLY 12,238 57 km
2009 CORRAL 12,006 71 km
1996 SCOTT 8,828 50 km
2015 WRAGG 8,455 63 km
2003 BIRD 7,727 76 km
2014 MONTICELLO 6,984 66 km
1984 SITE 300 3 6,911 65 km
Source: NIFC/IRWIN Wildfire Records (100+ acres).

Monthly Weather

Month Avg Temperature Precipitation Summary
January 48°F (9°C) 3.6 in Wettest
February 51°F (10°C) 3.2 in
March 54°F (12°C) 2.7 in
April 59°F (15°C) 0.9 in
May 65°F (18°C) 0.5 in
June 70°F (21°C) 0.1 in
July 76°F (24°C) 0.0 in Warmest, Driest
August 72°F (22°C) 0.1 in
September 70°F (21°C) 0.3 in
October 63°F (17°C) 0.9 in
November 52°F (11°C) 2.4 in
December 45°F (7°C) 2.5 in Coldest

Thornton has a seasonal temperature swing of 31°F / from 45°F in December to 76°F in July. Total annual precipitation is 17.2 inches, with January being the wettest month (3.6") and July the driest (0.0").

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