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Climate in Eureka, California: Monthly Weather Averages

By the AverageClimate Editorial Team · Last updated: October 2026

Eureka sits at 20 feet above sea level, and its climate, as recorded at the Eureka Weather Forecast Office Woodley Island, CA station, runs to a yearly mean of 52.6°F. The warmest month is August, averaging 58.5°F with typical highs of 64.0°F; the coldest is December, averaging 47.4°F with lows around 40.0°F. Across a normal year the city receives 40.4 in of precipitation and 0.0 in of snow. The full month-by-month picture below comes from the official 1991–2020 U.S. Climate Normals — the 30-year averages the National Weather Service itself uses — so it describes the Eureka climate you should actually plan around, whether you are timing a visit, weighing a move, or just settling an argument about which month is best.

Eureka climate month by month

The table below is the complete 1991–2020 normals profile for Eureka: average high, average low and mean temperature, rainfall, and snowfall for every month. Read down the Mean column to feel the year's rhythm — Eureka's temperature range runs from 47.4°F in December to 58.5°F in August.

How to read the colors:below freezingcoldcoolmildwarmhot. Bands are colored by each cell's own temperature, so a whole year reads at a glance.

Eureka through the seasons

Winter in Eureka averages highs of 54.7–55.4°F and lows of 40.0–41.3°F, a seasonal mean of 47.9°F. The three months together bring 20.4 in of precipitation — about 51% of the city's yearly total — with December the wettest of the three at 8.10 in. Winters here are cool rather than harsh: chilly mornings, mild afternoons, and only occasional brushes with freezing weather.

Spring in Eureka averages highs of 56.1–59.6°F and lows of 42.4–47.7°F, a seasonal mean of 51.2°F. The three months together bring 11.1 in of precipitation — about 27% of the city's yearly total — with March the wettest of the three at 5.75 in. The season is a transition: the average temperature climbs 4.5°F from March to May, and by late spring Eureka is firmly into mild territory.

Summer in Eureka averages highs of 61.9–64.0°F and lows of 50.1–53.0°F, a seasonal mean of 57.4°F. The three months together bring 1.1 in of precipitation — about 3% of the city's yearly total — with June the wettest of the three at 0.70 in. Summer is the mildest in the country by big-city standards — heat waves happen, but the average afternoon stays in the 70s, and many homes historically get by without air conditioning.

Fall in Eureka averages highs of 57.8–63.9°F and lows of 43.2–50.5°F, a seasonal mean of 54.0°F. The three months together bring 7.9 in of precipitation — about 20% of the city's yearly total — with November the wettest of the three at 4.89 in. Temperatures ease off through the season — the monthly mean drops 6.7°F from September to November — and fall is when Eureka's weather turns crisp and dry, while nights stay mostly frost-free into December.

Best and worst months to visit Eureka

Ranking every month by its normals — mild mean temperatures score best, heavy rain and snow count against — the most comfortable months to visit Eureka are:

JulyAugustSeptember

July leads the list: average highs of 63.1°F, lows of 52.4°F, and 0.18 in of rain, with snow a non-factor at 0.0 in. The other picks, August and September, offer the same balance in Eureka's mild stretch of the year. At the other end, December is usually the month to avoid — the year's heaviest rain, with a mean temperature of 47.4°F and 8.10 in of precipitation.

How Eureka compares

Across the 114 cities in our dataset, the typical city averages 57.8°F for the year and 35.7 in of precipitation. Eureka runs 5.2°F cooler than that typical city and wetter by 4.7 in a year, ranking #75 of 114 for annual warmth and #52 of 114 for precipitation (wettest first). Its year-round temperature swing — warmest month minus coldest — is 11.1°F, which puts it in the mild, ocean- or latitude-softened camp.

Within California, Eureka is the coolest of the cities we track. See the California climate overview for the full state comparison, including Fresno (warmest, 65.0°F yearly mean) and Eureka (coolest, 52.6°F).

Planning notes for Eureka

For anyone relocating: average lows never drop below freezing in any month, so hard freezes are events, not seasons; even the warmest month's average high stays below 80°F, so summer heat is rarely a planning factor; 4 months of the year average between 55°F and 80°F, the band most people find comfortable without heating or cooling. Those four facts, all straight from the normals table above, shape everything from a Eureka wardrobe to its utility bills.

Eureka climate FAQ

Source: 1991–2020 U.S. Climate Normals, NOAA National Centers for Environmental Information (NCEI) — ncei.noaa.gov. Station: Eureka Weather Forecast Office Woodley Island, CA (USW00024213), elevation 20 ft. Figures checked October 2026.