Last updated: February 24, 2025
In September, Sonoma experiences a delightful range of temperatures, with a maximum reaching 39°C (102°F) and a comfortable average of 20°C (68°F). The nights bring a refreshing coolness, dipping to a minimum of 9°C (48°F). The month sees an almost dry spell, recording a mere 1 mm of precipitation with no rain days. Despite the warmth, humidity levels linger around 68%, contributing to a pleasant climate perfect for enjoying the region's renowned vineyards and outdoor activities.
In September, Sonoma experiences a delightful transition with temperatures that reflect the lingering warmth of summer. The minimum temperature settles at a mild 9°C (48°F), while the average remains pleasant at 20°C (68°F). However, the month’s highlight is the peak, which can soar to a scorching 39°C (102°F), making it one of the hottest times of the year. This notable rise compared to previous months signals that the region enjoys a final burst of summer heat before the fall chill sets in. As the days gradually shorten, Sonoma's vibrant scenery and lush vineyards create an inviting atmosphere, perfect for indulging in outdoor activities or savoring local wines.
September in Sonoma sees a noticeable shift as the summer heat begins to wane. With only 1 mm of precipitation recorded, there is a stark contrast from the wetter months earlier in the year. Notably, September records no rainy days, reflecting the culmination of the dry summer months, which includes July and August where precipitation was nonexistent. This trend underscores a seasonal pattern where late summer often yields minimal rainfall, paving the way for the more temperate fall months. As October approaches, residents can expect a return to more typical precipitation levels, signaling the transition towards the wetter season ahead.
As summer gives way to autumn, September in Sonoma reveals a shift in humidity levels, hovering around 68%. This slight increase from the drier months of July and August, which saw lows of 70% and 66% respectively, signifies a gradual return to the more humid conditions typical of the fall. The trend suggests a gradual rebound toward the higher humidity levels experienced earlier in the year—peaking at 86% in January. Overall, September's humidity serves as a gentle reminder of the transition to cooler, moister months, inviting residents and visitors alike to enjoy the scenic landscapes with a touch more comfort.
In Sonoma, United States, the UV Index during September reflects a significant trend observed throughout the year, showcasing an end-of-summer transition. With a UV Index of 9, categorized as very high, this month requires careful sun exposure management, allowing for a burn time of just 15 minutes. As summer peaks in June and July with UV Index readings of 11 (extreme), the gradual decline in intensity through August and September indicates a seasonal shift, yet still calls for vigilance. This period serves as a reminder to prioritize sun safety, as the sun's strength remains formidable. To learn more about UV Index trends in Sonoma, check out Sonoma UV Index.
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As summer fades, September brings a delightful balance of sunshine to Sonoma, with 314 hours of radiant light gracing the region. This month serves as a gentle transition from the peak warmth of July, which tops the year at 394 hours, to the cooler embrace of fall in October, where sunshine dips to 280 hours. The consistent decline in daylight hours from the summer months is evident as activity shifts from sun-soaked days to the harvest season. However, September still holds onto a significant amount of brightness, making it an ideal time to explore Sonoma's vineyards and enjoy outdoor festivities before autumn claims the days. The month reflects a harmonious blend of lingering summer warmth and the anticipation of the crispness to come, creating a captivating atmosphere that enchants both locals and visitors alike.
As summer gracefully transitions into autumn, Sonoma, California experiences a delightful trend in sunny weather, particularly in September, where the chance of sunshine stands at a comfortable 73%. This follows the peak of 82% in May, showcasing the lingering warmth of the summer months. June and July maintain a solid 78% and 71%, respectively, before August dips slightly to 75%. With October bringing a significant drop to 52%, September offers a sweet spot for sun-seekers, blending the final warmth of summer with the crisp beginnings of fall. Overall, this month is an inviting time for outdoor adventures, providing plenty of opportunities to soak in the beautiful California sun.
As summer fades into autumn, September in Sonoma, United States, welcomes a gentle decline in daylight duration, dipping to 12 hours after basking in the 14-hour glory of the preceding months. This shift marks a transition from the peak summer brightness of June through August, where sunlight graced the region consistently. Interestingly, September’s daylight serves as a bridge, still offering ample time to enjoy outdoor activities while hinting at the approaching shorter days of fall. As the month progresses, daylight gradually recedes, ushering in the cozy atmosphere of autumn, characterized by a slow and steady retreat into longer evenings and shorter afternoons, ultimately leading into the brisk days of October.
In September, Sonoma experiences a gentle return to calmer breezes, with an average wind speed of 2.1 m/s (5 mph)—mirroring the tranquility of January's winds. This slight dip follows a modest peak in May at 3.2 m/s (7 mph) and reflects a broader trend of diminishing winds as summer transitions into fall. Throughout the warmer months, particularly in June and July, wind speeds hover near the 3 m/s mark, providing a vibrant backdrop for outdoor activities. As autumn approaches, however, September winds blend effortlessly with the serene Californian landscape, creating a peaceful ambiance that invites leisurely vineyard strolls and sunset picnics. The overall pattern suggests a rhythmic wind cycle, with the briskest speeds occurring in late spring, gradually tapering as the year draws to a close.
The weather in Sonoma changes throughout the year, offering a unique experience in each season. Below is a month-by-month comparison of September's weather with other months, highlighting differences in temperature, precipitation, and other key factors. Click on each section to discover seasonal trends in Sonoma and find detailed weather information for every month.
September and January showcase contrasting weather conditions. In September, the temperatures range from a minimum of 9°C (48°F) to a soaring maximum of 39°C (102°F), with an average of 20°C (68°F) and virtually no precipitation, making it a dry month with humidity around 68%. In stark contrast, January experiences much cooler temperatures, with a minimum of -1°C (31°F) and a maximum of 24°C (76°F), averaging only 10°C (50°F). This winter month is marked by significant rainfall, accumulating 125 mm (4.9 in) over 9 days, and higher humidity levels of 86%. For a deeper understanding of the weather during this time, you can explore more about Sonoma weather in January.
In September, temperatures typically range from a cool 9°C (48°F) at night to a sweltering maximum of 39°C (102°F) during the day, with an average of 20°C (68°F). The month is characterized by minimal precipitation, with little to no rain, and a humidity level of 68%. In stark contrast, February experiences much cooler temperatures, with nights dropping to -1°C (30°F) and daytime highs reaching 26°C (79°F), averaging around 11°C (52°F). This month is significantly wetter, receiving about 127 mm (5.0 in) of rainfall over approximately 8 days, and features higher humidity at 84%. For a closer look at February's conditions, you can visit Sonoma weather in February.
September and March offer stark contrasts in weather. September boasts milder temperatures, with lows around 9°C (48°F) and highs reaching an impressive 39°C (102°F), typically accompanied by low precipitation and lower humidity at 68%. In contrast, March experiences cooler conditions, with minimum temperatures of just 1°C (34°F), an average of 12°C (54°F), and maximums of 27°C (80°F). This month sees significantly more rainfall, totaling 84 mm (3.3 in) over approximately 10 days, along with higher humidity levels at 83%. For a detailed look at the weather specifics, check out Sonoma weather in March.
In September, the weather tends to be warm and dry, with average temperatures around 20°C (68°F) and maximum highs reaching up to 39°C (102°F). The month typically sees little to no precipitation, with a humidity level of 68%. In contrast, April is cooler and more humid, with average temperatures around 14°C (58°F) and maximum highs of 30°C (86°F). This month experiences more rainfall, averaging 36 mm (1.4 in) over about five days, resulting in a humidity level of 80%. For more details on April weather, you can visit Sonoma weather in April.
September typically boasts warmer weather compared to May, with average temperatures reaching around 20°C (68°F) and maximums soaring up to 39°C (102°F). In contrast, May's weather is cooler, averaging about 17°C (62°F) and peaking at a maximum of 34°C (93°F). While September enjoys almost no precipitation with just 1 mm recorded over the month, May experiences more rainfall at 21 mm over three days. Additionally, humidity levels in May are slightly higher at 80%, compared to 68% in September. For a detailed look at May weather in Sonoma, you can visit Sonoma weather in May.
In comparing the weather of September and June, both months showcase similar average temperatures, both hovering around 20°C (68°F). However, September experiences slightly warmer conditions, with maximum temperatures reaching up to 39°C (102°F), compared to June's high of 37°C (99°F). While both months have very little precipitation, June tends to have a marginally higher humidity level at 76%, as opposed to September's 68%. For more detailed insights, you can check Sonoma weather in June.
In comparing the weather of September to that of July, both months exhibit mild averages of around 20°C (68°F), with September experiencing slightly more variability in temperature. September showcases a wider temperature range, with lows dropping to 9°C (48°F) and highs reaching up to 39°C (102°F), while July remains a bit warmer overall, with temperatures ranging from 11°C (53°F) to a maximum of 36°C (96°F). Precipitation in both months is virtually non-existent, with September seeing only 1 mm and July having none. Humidity levels are fairly comparable, with September at 68% and July just a tad higher at 70%. For a more detailed look at July's conditions, you can check out Sonoma weather in July.
In comparing the weather of September and August, we see a gradual transition in temperatures and humidity. September recorded a minimum temperature of 9°C (48°F) and a maximum of 39°C (102°F), while August had slightly higher minimum temperatures at 11°C (52°F) and a maximum of 36°C (98°F). Both months experienced very little precipitation, with September receiving just 1 mm over the entire month and August having none at all. Humidity levels were also comparable, with September at 68% and August slightly lower at 66%. For more detailed weather insights, check Sonoma weather in August.
September's weather offers a warm retreat with an average temperature of 20°C (68°F) and a striking maximum of 39°C (102°F), while enjoying relatively low precipitation and humidity at 68%. In contrast, October brings cooler temperatures, with a minimum of 4°C (40°F) and an average of 17°C (63°F). This month also sees an increase in rainfall, totaling 33 mm (1.3 in) over 2 days, and a slight rise in humidity to 72%. For more details, check out Sonoma weather in October.
September and November showcase a stark contrast in weather. In September, temperatures range from a minimum of 9°C (48°F) to a sizzling maximum of 39°C (102°F), with an average of 20°C (68°F). The month is notably dry, recording only 1 mm of precipitation over zero rainy days and maintaining a humidity level of 68%. Conversely, November brings cooler temperatures, with a minimum of 1°C (33°F), an average of 12°C (55°F), and a maximum of 27°C (81°F). This month experiences significantly more precipitation, totaling 50 mm (2.0 in) over five days, along with higher humidity at 84%. For a detailed look at the weather patterns in November, you can check out Sonoma weather in November.
In September, the weather in Sonoma is characterized by warm temperatures, with a minimum of 9°C (48°F) and an average high of 39°C (102°F), making it a hot month with virtually no precipitation. The humidity sits at a comfortable 68%, contributing to dry conditions ideal for outdoor activities. In stark contrast, December brings cooler temperatures, with a minimum of 0°C (33°F) and an average high of 23°C (73°F). This month also experiences significant precipitation, totaling 94 mm (3.7 in) over nine days, along with increased humidity at 84%. For more detailed insights, visit Sonoma weather in December.
As summer fades into autumn, September in Sonoma presents a delightful transition, characterized by warm temperatures and dry conditions. With an average temperature that hovers around a pleasant 20°C, this month sees the last bursts of heat, occasionally reaching up to 39°C. Unlike the wetter months that follow, September stands out with minimal precipitation—the region experiences virtually no rain, allowing for endless sunny days. The humidity level, while slightly elevated, adds to the crispness of the air, perfectly suited for vineyard explorations and outdoor activities. For a deeper dive into the climate patterns throughout the year, check out Sonoma Climate.