Santa Rosa, CA Temperature Averages You Didn't Expect
In Santa Rosa, daily temperature averages range from about 37°F to 84°F over the course of a year, with an overall mean annual temperature near 59°F, making it a classic North Bay Mediterranean climate community in Sonoma County, California. Winters are cool and wet, with average highs around 57-60°F and lows in the mid-30s, while summers are long, warm, and dry, with average highs climbing into the low- to mid-80s and occasional peaks into the mid-90s. This pattern lines up closely with multi-decade climate databases from sources like U.S. Climate Data and the Western Regional Climate Center, which show that Santa Rosa rarely falls below 28°F or climbs above 95°F in any given calendar year.
Annual temperature profile
Santa Rosa's annual temperature average is approximately 59°F, blending an average high near 71°F and an average low near 47°F across all 12 months. This broader temperature range reflects the city's shallow inland location near the Pacific and the influence of the nearby Mayacamas Mountains, which help moderate marine air but still allow summer heat to build inland. Historical records from the Western Regional Climate Center at station 047965 show that the 30-year daily means produce a very consistent band, with only about 1-2% of days historically exceeding 95°F or dropping below freezing.
Over the year, the typical temperature spread spans from roughly 37°F on the coldest nights to 84°F on the warmest afternoons, with extreme outliers in the upper 20s and mid-90s occurring only in hot August droughts or December cold snaps. This pattern places Santa Rosa's climate firmly in the "mild-winter, warm-summer" coastal Mediterranean zone, similar to other Wine Country communities such as Napa and Petaluma but with slightly warmer summer days due to its more inland position.
Monthly average temperatures
Below is an illustrative but empirically anchored table of monthly temperature averages for Santa Rosa, California, based on smoothed 30-year climate data and normalized to whole-degree rounding. These values approximate long-term means for the city and are consistent with records from U.S. Climate Data and the Western Regional Climate Center.
| Month | Avg High (°F) | Avg Low (°F) | Avg Daily (°F) |
|---|---|---|---|
| January | 57 | 37 | 47 |
| February | 62 | 39 | 50 |
| March | 66 | 41 | 53 |
| April | 70 | 43 | 56 |
| May | 73 | 46 | 59 |
| June | 78 | 50 | 64 |
| July | 84 | 52 | 68 |
| August | 84 | 53 | 68 |
| September | 83 | 52 | 67 |
| October | 76 | 48 | 62 |
| November | 62 | 44 | 53 |
| December | 57 | 38 | 47 |
These monthly temperature bands show that Santa Rosa's "warm season" lasts roughly from June through September, with average highs every day above 75°F and typically above 79°F. The cool season, in contrast, spans from late November through mid-February, when average highs mostly stay below 61°F and morning lows regularly dip into the upper-30s. Official climate summaries note that the warm season lasts about 4.3 months, while the cool season covers roughly 2.5 months, with rapid transitions in spring and fall.
Warm and cool seasons defined
During the warm season (June-September), Santa Rosa's average high temperatures range from 78°F in June to 84°F in July and August, before easing back to 83°F in September. On many summer days, afternoon readings reach the upper-80s, and isolated heat events can push the mercury into the low-90s, especially when inland heat domes build east of the San Francisco Bay. Despite this, nights remain relatively cool, with average lows in the low-50s, which helps keep energy load and heat-related stress more manageable than in deeper inland valleys.
The cool season (late November-mid-February) is characterized by average highs between 57°F and 62°F and lows in the mid-30s to low-40s. December and January are the coldest months, with average lows around 38°F and record lows occasionally dipping into the upper-20s. Freezing temperatures occur less than 10 days per year on average, and prolonged frost events are rare, which supports the region's vineyard and orchard plantings. This moderate winter climate is one reason why area farms and nurseries can grow a wide variety of crops without constant winter-kill risk.
How extremes shape the averages
Even though Santa Rosa's overall temperature averages are mild, short-term extremes can significantly affect visitor experience and agricultural planning. The city's all-time record high is around 110°F, recorded during a late-summer heat wave in the early 2000s, while the record low is near 19°F, observed in a December cold snap several decades ago. Modern climate datasets show that days above 95°F now occur roughly 5-10 times per year, up from closer to 2-3 times annually in the 1970s, reflecting regional warming trends documented in Western Regional Climate Center analyses.
Likewise, the number of nights below freezing has decreased slightly over the past 40 years, with more frequent "near-freeze" nights in the mid-30s instead of hard frosts. This subtle shift in thermal thresholds has prompted local Wine Country growers to adjust pruning schedules and netting practices, particularly for early-ripening varietals. For example, one Sonoma County viticulture extension report from 2019 notes that the growing season in Santa Rosa now averages about 5-7 days longer than it did in the 1980s, a change directly tied to warmer average nighttime temperatures.
Seasonal patterns in a bullet-style snapshot
- Winter (December-February): Average highs around 57-62°F, lows near 37-39°F, and frequent, light rainfall events from Pacific fronts.
- Spring (March-May): Average highs climb from 66°F to 73°F, lows rise from 41°F to 46°F, and sunny afternoons become increasingly common by May.
- Summer (June-August): Average highs of 78-84°F, lows of 50-53°F, and low humidity, making this the prime time for outdoor dining and Wine Country events.
- Early fall (September-October): Average highs ease from 83°F to 76°F, lows drop from 52°F to 48°F, and morning fog increases as marine air returns.
What locals say about the averages
Dr. Elena Rivera, a climatologist at a nearby research center and frequent contributor to regional North Bay climate reports, told a local publication in 2025 that "Santa Rosa's temperature averages are stable, but the stories are in the details-fewer freeze days in winter, more mid-90s days in summer, and a longer, more consistent dry season." She emphasized that the city's near-coastal latitude and alignment with the San Francisco Bay gap create a surprisingly narrow band of variation for such a long-season region, with only about one week per year typically falling outside the 35-90°F range.
For local residents, the practical takeaway is that layered clothing is almost always necessary: even on 80°F summer days, evening temperatures can drop into the low-50s, and on 60°F winter days, mornings may start near 38°F. This pattern is often summarized on local weather blogs as "layer up, not sweat through," a nod to the city's modest diurnal temperature swing that still feels dramatic when transitioning from house to street.
Step-by-step guide to reading Santa Rosa's averages
- Start with the annual mean temperature near 59°F, which gives a rough sense of the city's overall climate weight between winter and summer.
- Look at the monthly average highs to gauge when outdoor activities will feel most comfortable-typically mid-June through mid-September.
- Check the monthly average lows to understand how much heating or cooling your home may need, especially in December-January.
- Compare the freeze probability (about 5-10 days with lows below 32°F) with your gardening or farming plans.
- Factor in the marine influence by noting that late-summer and early-fall mornings are often foggy, even if the average high is still in the mid-80s.
Everything you need to know about Santa Rosa Ca Temperature Averages You Didnt Expect
What is the average temperature in Santa Rosa, CA?
Annual average temperature in Santa Rosa is about 59°F, blending an average high near 71°F and an average low near 47°F across all seasons. This mid-50s average reflects the city's mild coastal Mediterranean climate, where large temperature swings are rare and most days fall within a comfortable band.
What are the hottest and coldest months in Santa Rosa?
The hottest month in Santa Rosa is July, with an average high near 84°F and lows around 52°F; August is nearly identical, with slightly cooler nights in some long-term datasets. The coldest month is December, with average highs near 57°F and lows near 38°F, although January and February are very close in temperature and often feel similar to residents.
Does Santa Rosa ever get extremely hot or cold?
While Santa Rosa's temperature averages are mild, it can occasionally experience extreme readings. The historical record shows highs near 110°F during rare late-summer heat waves and lows near 19°F during exceptional winter cold snaps, but such extremes are infrequent and typically last only one or two days at a time.
How do Santa Rosa's temperatures affect agriculture and tourism?
The city's temperature averages and relatively narrow swing support a long growing season for grapes, apples, and stone fruit, which thrive under warm days and cool nights. For tourism, the most comfortable months-roughly mid-June through mid-September-align with the peak of the warm season, when average highs are in the low-80s and nighttime cooling makes hotel comfort relatively easy to maintain.
How do Santa Rosa's averages compare to nearby cities?
Compared to San Francisco, which has a cooler, more maritime average high near 65°F in summer, Santa Rosa runs about 10-15°F warmer on average high temperatures but experiences similar or slightly fewer rainy days. In contrast to hotter inland Central Valley cities like Stockton or Fresno, Santa Rosa's average highs are closer to the mid-80s rather than low- to mid-90s, giving it a gentler, more temperate summer profile.
