What is the hottest month in Hercules, CA?

September is the warmest month, with a normal high of 86°F at Vallejo.

What is the coldest month in Hercules, CA?

January is the coldest month, with a normal low of 42°F.

What is the wettest month in Hercules, CA?

December has the most precipitation on average, about 4.49 inches.

Checked Oct 25, 2026

Hercules, CA Climate

1991 to 2020 normals at Vallejo, 7.7 mi from the center of Hercules, elevation 341 ft.

Average weather by month

Select a month for daily normals and last year's weather

Month	High	Low	Precip.	Snow
January	57°	42°	4.46 in	--
February	63°	45°	3.58 in	--
March	68°	46°	3.18 in	--
April	73°	47°	1.45 in	--
May	78°	51°	0.80 in	--
June	83°	54°	0.22 in	--
July	85°	56°	0.00 in	--
August	86°	56°	0.04 in	--
September	86°	57°	0.08 in	--
October	79°	54°	1.02 in	--
November	66°	47°	2.17 in	--
December	58°	42°	4.49 in	--
Year	74°		21.49 in	--

Frequently asked questions

What is the hottest month in Hercules, CA?: September is the warmest month, with a normal high of 86°F at Vallejo.
What is the coldest month in Hercules, CA?: January is the coldest month, with a normal low of 42°F.
What is the wettest month in Hercules, CA?: December has the most precipitation on average, about 4.49 inches.

Today

Hercules, CA forecast

Data sources

U.S. Climate Normals 1991-2020NOAA National Centers for Environmental Information · Official site
U.S. Climate Normals 1991-2020 (daily) and GHCN-Daily via Access Data ServiceNOAA National Centers for Environmental Information · Official site

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About this data

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