Last updated: February 24, 2025
In September, Guerneville, California, experiences a mild climate characterized by an average temperature of 19°C (67°F), with extremes reaching a maximum of 40°C (103°F) and a minimum of 8°C (47°F). The month boasts zero precipitation days, accumulating only 2 mm (0.1 in) of rainfall, contributing to a relatively dry atmosphere. With a humidity level hovering around 68%, the weather is comfortably warm, making it an ideal time for outdoor activities and exploration of the scenic beauty of the region. Enjoy the vibrant autumnal hues as summer transitions into fall, perfect for adventure or relaxation.
In September, Guerneville experiences a delightful transition as summer gives way to early autumn. With minimum temperatures averaging around 8°C (47°F) and maximums soaring to a sizzling 40°C (103°F), the weather can be quite dynamic. The average temperature sits comfortably at 19°C (67°F), offering a pleasant balance that invites outdoor activities. As the month progresses, you'll notice slight fluctuations that hint at the cooler days ahead, making it an ideal time for both sun-soaked adventures and cozy evenings. Whether you're hiking through the vibrant fall foliage or enjoying a warm drink by the fire, September in Guerneville is a captivating blend of warmth and crispness.
In September, Guerneville experiences a significant drop in precipitation, reflecting the typical dry spell of late summer. With just 2 mm (0.1 in) of rain and no recorded precipitation days, September maintains the trend of minimal rainfall established in the preceding months of July and August, which both saw 0 mm of precipitation. This stark contrast to the wetter months of January and February, where rainfall exceeds 140 mm, highlights the region's seasonal shift. As autumn approaches in October, the expectation for increased rainfall returns, hinting at the cyclic nature of Guerneville's climate.
In Guerneville, United States, the humidity trends throughout the year reveal a fascinating ebb and flow. Starting strong in January with a high of 86%, the moisture gradually declines, hitting its annual low in August at 66%. As September rolls in, humidity begins to regain a bit of its prior strength, rising slightly to 68%. This uptick signals the transition towards the wetter months, as October sees a bump back to 72%. Overall, while the summer months bring lower humidity levels, September stands out as a transitional bridge, hinting at the return of the lush, humid conditions characteristic of the region's fall and winter.
As summer fades in Guerneville, September brings a UV Index of 9, categorized as very high, with a burn time of just 15 minutes. This trend captures the lingering intensity of the sunny season, following the peak months of July and August, where the UV Index reached its maximum at 11. As we transition into fall, the UV Index starts to decrease, but September still demands caution for sun exposure. It's crucial for residents and visitors alike to stay vigilant, protect their skin, and enjoy the beauty of this vibrant time of year. For more details, check out the Guerneville UV Index.
UV Risk Categories
As summer gives way to fall, September in Guerneville offers a delightful blend of warmth and sunshine, with 306 hours of bright daylight—a notable decline from the peak of 375 hours in July but still robust enough to enjoy the great outdoors. The gradual fading of sunlight in these early autumn months is a gentle transition from the vibrancy of summer, where May and June basked in their longest daylight stretches. With the days becoming shorter yet still holding onto the warmth, September invites residents and visitors alike to savor the stunning landscapes and lingering golden hours before the cooler months arrive. As October approaches, with its 275 hours of sunlight, there's a palpable sense of change in the air, making September a unique time to relish late-season adventures and vibrant autumn hues.
September in Guerneville transitions into autumn with a 72% chance of sunny weather, maintaining a robust opportunity for outdoor enjoyment. This figure reflects a slight dip from the peak summer months of July and August, which enjoy around 79% to 80% sunshine. However, it still stands strong compared to the earlier months of the year, such as 39% in January and 58% in February. As summer winds down, September retains a significant chance of clear skies, making it an inviting time for visitors seeking to bask in the remaining warmth before the fall sets in.
As summer fades and September arrives in Guerneville, the days begin to shorten, with daylight lasting approximately 12 hours. This marks a gentle decline from the peak of 14 hours seen in the height of summer, reflecting the natural rhythm of the seasons. The warm, lingering evenings give way to a gradual transition towards autumn, where each day becomes incrementally shorter. This shift not only alters the landscape's beauty but also invites residents and visitors alike to savor the stunning sunsets and the vibrant hues of the changing leaves, as nature prepares for the cooler months ahead. September's daylight hours serve as a reminder of the cyclical patterns of our environment, blending the remnants of summer with the promise of fall.
As the summer blends into early autumn in Guerneville, September brings a gentle breeze, with an average wind speed of 2.3 m/s (5 mph). This slight dip from the more vigorous breezes of May and June, which peak at 4.1 m/s (9 mph), suggests a gradual transition into the quieter months of the year. Following a consistent pattern, the wind tends to soften during late summer, with both July and August maintaining the same leisurely pace of 2.4 m/s (5 mph). As days shorten and temperatures cool, the wind often carries a hint of change, paving the way for the more dynamic gusts of October that average 2.7 m/s (6 mph). Thus, September in Guerneville is characterized by its tranquil winds, reflective of the serene atmosphere that envelops this charming locale as summer bids farewell.
The weather in Guerneville 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 Guerneville and find detailed weather information for every month.
September and January present stark contrasts in weather. In September, temperatures can soar as high as 40°C (103°F), with an average of 19°C (67°F) and minimal precipitation of just 2 mm, which is typical for the dry season. The humidity levels hover around 68%, making the heat feel quite intense at times. In contrast, January offers cooler temperatures, with a minimum of -1°C (30°F) and a maximum of 25°C (77°F), resulting in an average of 10°C (50°F). This month is characterized by significantly higher precipitation at 140 mm (5.5 in) over about 9 days, coupled with increased humidity levels of 86%. These differences highlight the transition from the warmth of late summer to the chill and moisture of winter. For more detailed insights into the January weather, you can visit Guerneville weather in January.
Comparing the weather in September and February reveals stark contrasts in temperature and precipitation. In September, temperatures can soar as high as 40°C (103°F), with an average of 19°C (67°F), while February features much cooler conditions, with a maximum of 25°C (77°F) and an average of 10°C (51°F). September typically experiences dry weather with no recorded precipitation, whereas February is quite the opposite, bringing significant rainfall of 157 mm (6.2 in) over approximately eight days. Moreover, humidity levels are higher in February at 84%, compared to 68% in September. For more detailed insights, you can check out Guerneville weather in February.
September and March present quite different weather experiences. In September, temperatures can soar as high as 40°C (103°F), with an average of 19°C (67°F) and very little precipitation—only about 2 mm throughout the month, and typically no rainy days, resulting in a relatively comfortable humidity level of 68%. In contrast, March is much cooler, with average temperatures around 11°C (52°F) and maximums reaching 26°C (80°F). It also sees considerably more rainfall, totaling 96 mm over approximately 10 rainy days, leading to higher humidity levels of 83%. To explore more about the weather in March, you can visit Guerneville weather in March.
In September, temperatures can soar to highs of 40°C (103°F), with an average of 19°C (67°F) and minimal precipitation, experiencing just 2 mm (0.1 in) over no rainy days. This results in relatively lower humidity levels at 68%. In contrast, April sees cooler weather with an average temperature of 13°C (57°F) and maximums reaching 30°C (86°F). April also tends to be wetter, with 47 mm (1.9 in) of precipitation spread over approximately 6 rainy days, leading to higher humidity at 80%. For more detailed information, you can check Guerneville weather in April.
When comparing the weather in September and May, notable differences emerge. September boasts a wider temperature range with a minimum of 8°C (47°F) and a maximum that can reach up to 40°C (103°F), averaging around 19°C (67°F). In stark contrast, May features cooler temperatures, with a minimum of 5°C (41°F) and a maximum of 33°C (91°F), averaging 16°C (60°F). Additionally, September enjoys a drier climate with virtually no precipitation, while May experiences more humidity at 80% and around 30 mm (1.2 in) of rainfall spread over three days. For more detailed information on May weather, you can visit Guerneville weather in May.
September and June exhibit similar average temperatures, both averaging around 19°C (67°F), but September can experience slightly higher maximum temperatures, peaking at 40°C (103°F) compared to June's maximum of 37°C (99°F). Both months are characterized by low precipitation with just 2 mm (0.1 in) and no rainy days recorded. However, September tends to be less humid at 68%, while June is more humid at 76%, contributing to a different overall feel in the atmosphere. For a more detailed look at June weather, you can visit Guerneville weather in June.
In comparing the weather between September and July, September showcases a wider temperature range, with a minimum of 8°C (47°F), an average of 19°C (67°F), and a peak of 40°C (103°F). Despite this dramatic high, the month experiences very low precipitation at just 2 mm (0.1 inches) over no days of rain, and a humidity level of 68%. In contrast, July has a slightly higher minimum temperature of 11°C (53°F), an average of 20°C (68°F), and a maximum of 35°C (95°F). It also remains dry, with no recorded precipitation and humidity at 70%. For more information on July weather, check out Guerneville weather in July.
In comparing the weather between August and September, September showcases a wider temperature range, with minimums dropping to 8°C (47°F) and maximums soaring to 40°C (103°F), compared to August's more moderate range of 10°C (50°F) to a maximum of 35°C (96°F). Precipitation remains minimal in both months, but September records just 2 mm (0.1 in) over the course of 0 rainy days, while August experienced completely dry conditions with 0 mm (0.0 in) of precipitation as well. Humidity levels slightly increase in September at 68% compared to 66% in August. For a detailed look at August weather, you can check out Guerneville weather in August.
September tends to be quite warm, with temperatures averaging 19°C (67°F) and peaking at a high of 40°C (103°F). The month is characterized by very little precipitation, with only 2 mm recorded over no rainy days, and humidity levels around 68%. In contrast, October brings a noticeable drop in temperatures, with an average of 16°C (62°F) and a maximum of 35°C (94°F). This month also sees increased precipitation, totaling 43 mm over two days, and a slight rise in humidity to 72%. For more detailed weather insights, you can check out Guerneville weather in October.
September and November present a stark contrast in weather patterns. In September, temperatures can soar with a maximum of 40°C (103°F) and an average of 19°C (67°F), while precipitation is nearly nonexistent with only 2 mm recorded. The humidity sits at 68%, contributing to a warm and dry atmosphere. In contrast, November cools down significantly, with temperatures ranging from a minimum of -1°C (30°F) to a maximum of 27°C (81°F) and an average of 12°C (54°F). This month also experiences much more precipitation, totaling 61 mm over approximately 5 days, and higher humidity at 84%. For more detailed information about the weather in this month, check Guerneville weather in November.
In September, the weather is characterized by warmer temperatures, ranging from a low of 8°C (47°F) to a high of 40°C (103°F), with an average temperature of 19°C (67°F). With minimal precipitation of just 2 mm (0.1 in) over the course of the month and a humidity level of 68%, the overall feel is quite dry and warm. In contrast, December brings a significant drop in temperature, with a minimum of 0°C (32°F) and an average of 9°C (49°F), peaking at 24°C (75°F). This winter month sees a substantial increase in precipitation, totaling 102 mm (4.0 in) over 9 rainy days, and a rise in humidity to 84%, making the atmosphere feel much cooler and wetter. For more details, check out the Guerneville weather in December.
September in Guerneville typically stands out as a tranquil transition from the heat of summer to the cooler embrace of autumn. With minimal precipitation and no rain days, the month offers a dry and pleasant climate, perfect for outdoor exploration. While maximum temperatures can soar to a sizzling 40°C, the average remains a comfortable 19°C, allowing residents and visitors to enjoy the beauty of nature without the extremes often experienced in July and August. The humidity, slightly elevated at 68%, adds a touch of warmth, making the evenings particularly inviting. For more insights into the overall climate trends in this charming locale, check out Guerneville Climate.