Weather & Climate in Half Moon Bay, CA

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

Half Moon Bay experiences four distinct seasons with an average annual temperature of 55°F (13°C). Winters average 51°F in January while summers reach 59°F in July / relatively mild seasonal variation. The area gets 323 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 26.0 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 39 feet.

Temperature

51°F Jan (11°C) 59°F Jul (15°C)

Annual Average	54.9°F
	2% above US avg
January Average	51°F (11°C)
July Average	59°F (15°C)
Sunny Days	323 days/yr

Geography

Elevation	39 ft (12 m)
Area	6.4 sq mi (16.7 km²)
Population Density	1,836/sq mi
Coordinates	37.4673°N, 122.4405°W
Timezone	America/Los_Angeles
County	San Mateo County County
Nearest Airport	San Francisco International (SFO) 11 miles away

Precipitation & Snow

Annual Rainfall 26.0"

31% below US avg

Snowfall 0.0"

Wettest Month (Jan) 5.87"

Driest Month (Jul) 0.12"

Air Quality

AQI Median	48.0
Rating	Good

Natural Hazard Risk

Overall Risk	Relatively High
Risk Score	99.2 / 100
Social Vulnerability	20.5 / 100
Community Resilience	97.6 / 100

Hazard Breakdown

Tornado	Relatively Low
Earthquake	Relatively High
Wildfire	Relatively Moderate
Flood	Relatively High
Hail	Very Low
Strong Wind	Relatively Low
Heat Wave	Relatively Moderate
Winter Weather	Very Low
Lightning	Relatively Moderate
Drought	Relatively High
Cold Wave	No Rating
Landslide	Relatively High
Coastal Flood	Relatively High
Tsunami	Relatively Moderate

Source: FEMA National Risk Index v1.20 (Dec 2025)

Earthquake History

4,284 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	84 km	11 km
Apr 18, 1990	5 km NNW of Aromas, California	M5.4	91 km	5 km
Aug 12, 1998	10 km SW of Ridgemark, California	M5.1	118 km	9 km
Apr 18, 1990	4 km E of Interlaken, California	M5.1	88 km	7 km
Jan 16, 1993	9 km E of Gilroy, California	M4.9	100 km	7 km
Sep 3, 2000	5 km WSW of Yountville, California	M4.9	101 km	9 km
Apr 23, 1995	22 km NNE of Soledad, California	M4.9	146 km	7 km
Apr 18, 1990	4 km NNW of Aromas, California	M4.9	92 km	6 km
May 14, 2002	5 km SSW of Gilroy, California	M4.9	93 km	7 km
Apr 19, 1996	2 km E of Aromas, California	M4.9	98 km	5 km
Sep 4, 1995	13 km SW of Middletown, California	M4.8	138 km	7 km
May 21, 1996	8 km ESE of East Foothills, California	M4.7	65 km	8 km
Apr 18, 1990	4 km N of Aromas, California	M4.7	93 km	4 km
Aug 11, 1993	14 km ESE of Alum Rock, California	M4.7	70 km	9 km
Aug 27, 2011	21 km NE of Soledad, California	M4.6	149 km	8 km
Aug 18, 1999	0 km S of Bolinas, California	M4.6	54 km	8 km
Mar 24, 1991	1 km NNE of Interlaken, California	M4.6	84 km	15 km
Sep 19, 2023	15 km SW of Westley, CA	M4.5	101 km	4 km
Jan 12, 2011	9 km SSE of San Juan Bautista, California	M4.5	114 km	8 km
Aug 3, 2006	5 km W of Glen Ellen, California	M4.5	101 km	9 km

Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.

Tornado History

32 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF2. Total: 9 injuries.

Date	Rating	Distance	Path	Fatalities
May 5, 1998	EF2	38 km	0.6 mi	0
Jan 11, 1951	EF2	30 km	5.7 mi	0
Dec 14, 2024	EF1	59 km	0.3 mi	0
Jan 23, 2010	EF1	77 km	1.6 mi	0
Mar 20, 2005	EF1	20 km	3.0 mi	0
Dec 20, 2001	EF1	81 km	0.5 mi	0
May 5, 1998	EF1	30 km	0.3 mi	0
Dec 23, 1996	EF1	97 km	6.0 mi	0
Jan 14, 1980	EF1	50 km	0.3 mi	0
Apr 1, 1965	EF1	78 km	0.1 mi	0
Apr 1, 1958	EF1	19 km	0.2 mi	0
Jan 6, 2019	EF0	68 km	0.5 mi	0
Jan 6, 2019	EF0	67 km	0.1 mi	0
Dec 22, 2012	EF0	85 km	1.1 mi	0
Apr 7, 2011	EF0	91 km	0.1 mi	0
Apr 14, 2007	EF0	91 km	0.2 mi	0
Dec 26, 2005	EF0	94 km	0.3 mi	0
Dec 5, 1998	EF0	66 km	1.0 mi	0
Dec 5, 1998	EF0	52 km	1.5 mi	0
May 12, 1998	EF0	89 km	0.2 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	40 km
1989	N. CALIFORNIA	Earthquake	1.0 m	62	69 km
1856	N. CALIFORNIA	Eruption + Earthquake	0.6 m	—	13 km
1906	N. CALIFORNIA	Eruption + Earthquake	0.1 m	—	26 km
1865	N. CALIFORNIA	Eruption + Earthquake	—	—	56 km

Source: NOAA/NCEI Historical Tsunami Database.

Nearby Volcanoes

1 volcano within 200 km. Closest: Clear Lake (170 km).

Name	Type	Elevation	Last Eruption	Distance
Clear Lake	Volcanic field	1,439 m (4,721 ft)	Unknown	170 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	83 km
2020	CZU AUG LIGHTNING	85,894	41 km
2017	NUNS	56,883	98 km
2007	LICK	47,424	94 km
2006	CANYON	36,851	98 km
2024	CORRAL	16,138	89 km
2009	CORRAL	12,006	85 km
1995	VISION	11,931	74 km
1985	LEXINGTON	11,550	59 km
2009	LOCKHEED	8,287	47 km
2003	BIRD	7,727	98 km
1984	SITE 300 3	6,911	88 km
2005	TESLA	6,638	80 km
2003	DEL PUERTO	6,441	92 km
2006	MIDWAY	6,243	84 km
2003	DEVIL	4,975	77 km
2020	WOODWARD	4,952	71 km
2003	JUMP	4,817	82 km
2016	LOMA	4,380	68 km
2008	WILD	4,100	96 km

Source: NIFC/IRWIN Wildfire Records (100+ acres).

Monthly Weather

Month	Avg Temperature	Precipitation	Summary
January	51°F (11°C)	5.9 in	Wettest
February	51°F (11°C)	4.7 in
March	52°F (11°C)	4.7 in
April	54°F (12°C)	2.2 in
May	56°F (13°C)	0.6 in
June	59°F (15°C)	0.2 in
July	59°F (15°C)	0.1 in	Driest
August	62°F (17°C)	0.2 in
September	62°F (17°C)	0.4 in	Warmest
October	59°F (15°C)	1.8 in
November	54°F (12°C)	4.3 in
December	50°F (10°C)	4.7 in	Coldest

Half Moon Bay has a seasonal temperature swing of 12°F / from 50°F in December to 62°F in September. Total annual precipitation is 29.7 inches, with January being the wettest month (5.9") and July the driest (0.1").

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