Last updated: February 24, 2025
In September, San Jose experiences a dynamic weather spectrum, with maximum temperatures soaring to an impressive 41°C (106°F) while maintaining a comfortable average of 19°C (67°F). The evenings can bring a cool respite, dipping to a minimum of 7°C (45°F). Residents and visitors can enjoy nearly uninterrupted sunshine, as the city records only 3 mm (0.1 in) of precipitation, with 0 days of rain throughout the month. With humidity hovering around 55%, the climate remains pleasant, making it an ideal time for outdoor activities and exploration.
In September, San Jose experiences a delightful transition as summer begins to wane. With minimum temperatures around 7°C (45°F) and an average of 19°C (67°F), the city enjoys comparatively mild weather. However, the real highlight is the peak temperatures soaring to a sizzling 41°C (106°F), making this month one of the hottest of the year. As the first hints of autumn approach, daytime warmth invites outdoor activities while cooler evenings provide relief, creating a perfect blend of summer's last warmth with the gentle onset of fall. This month stands out not just for its heat but also for the gradual shift towards more temperate conditions, preparing residents for the cooler months ahead.
In September, San Jose experiences a notable lull in precipitation, with a mere 3 mm (0.1 in) of rainfall recorded throughout the month. This minimal amount of rainfall is consistent with the summer trend, where July and August see 0 mm of precipitation, resulting in a dry spell that stretches across several months. The transition into autumn, marked by a slight uptick in precipitation in October at 25 mm (1.0 in), signals the onset of the wetter season ahead. Overall, September's dryness is a contributing factor to the region’s striking seasonal variability, as it gears up for the more moisture-laden months that follow.
As the summer heat fades into autumn, September in San Jose experiences a noticeable shift in humidity levels, dropping to 55%. This marks one of the lowest points of the year, following the dry months of July and August, which boast even lower humidity at 58% and 54%, respectively. However, as the city transitions into October, a gradual increase can be seen with humidity rising to 62%. Overall, September serves as a crucial turning point, where the air becomes crisper and drier, providing a refreshing reprieve before the return of higher humidity levels in late fall and winter. This trend underscores the area's distinct seasonal variations, perfect for those who appreciate the gentler embrace of early autumn.
As the summer wanes and September arrives in San Jose, residents can expect a very high UV Index of 9, along with a reduced burn time of 15 minutes. This marks a slight decrease from the intense, extreme conditions of the preceding months, reflecting the gradual transition from peak sunlight exposure. Following the extreme levels of UV Index 11 recorded in May through July, September brings a welcome reprieve, yet the caution remains; protective measures are still essential to avoid skin damage. As autumn begins to creep in, the UV levels will further decline in October, but for now, vigilance is key for outdoor enthusiasts. For more detailed information, check out the San Jose UV Index.
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As summer gently yields to autumn, September in San Jose shines brightly with 310 hours of sunlight, marking a charming transition from the peak summer months. After basking in an impressive 379 hours in July, the days begin to shorten, but the warmth lingers, with September still boasting a generous amount of sun. This month's sunlight is a delightfully vibrant contrast to the earlier winter months, showcasing a gradual decline in brightness as the year shifts—swinging from 360 hours in May to 206 hours in December. In essence, September encapsulates the essence of summer's warmth while hinting at the cool embrace of fall, offering a perfect backdrop for outdoor activities and community events.
In San Jose, September marks a delightful transition into autumn, boasting a sunny weather likelihood of 80%. This places it just below the peak summer months, where August enjoys an impressive 84% chance of sunshine. As summer fades, the consistent warmth remains, making September a fantastic time for outdoor activities under the clear blue skies. The likelihood of sunshine dips slightly in the following months, with October falling to 58%, so it's a prime opportunity to soak in the last rays of summer before the cooler, cloudier days set in. Overall, September provides a perfect blend of warmth and brightness, ideal for both residents and visitors alike.
As September arrives in San Jose, the warmth of summer begins to wane, reflected in the gradual decrease of daylight to 12 hours. This month's daylight marks a subtle transition; following the peak of 14 hours experienced during the summer months of June through August, September ushers in shorter days while still retaining a generous amount of sunlight. The trend is clear: as the year progresses from January's 9 hours of daylight, daylight hours steadily increase until they reach their zenith in summer, only to gradually taper off again, leading into the cozy, shorter days of fall and winter. This cyclical dance of daylight offers residents a beautiful blend of sun-soaked days and enchanting evenings as they transition into autumn.
As summer gracefully fades into autumn, September in San Jose experiences a gentle shift in its breezy character, with average wind speeds settling at 1.6 m/s (4 mph). While this is a slight increase from the lowest points of July and August, it marks a stable and tranquil period, reminiscent of the calm before the seasonal change. Notably, the wind patterns remain consistent throughout the year, generally hovering around 2.1 m/s to 2.2 m/s during the cooler months, while the summer months bring quieter breezes. This steady wind backdrop in September enhances the region's charm, inviting residents and visitors alike to relish in the mild, refreshing air as the vibrant colors of fall begin to emerge.
The weather in San Jose 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 San Jose and find detailed weather information for every month.
September and January present contrasting weather patterns. September boasts a broader temperature range, with minimums around 7°C (45°F) and maximums soaring to 41°C (106°F), coupled with minimal precipitation of just 3 mm (0.1 in) and no rainy days, resulting in a moderate humidity level of 55%. In stark contrast, January sees cooler temperatures, with minimums dropping to 0°C (32°F) and average highs around 24°C (75°F). The month is significantly wetter, receiving 145 mm (5.7 in) of rainfall over 8 days, and experiences higher humidity at 82%. For additional insights on January weather, visit San Jose weather in January.
September weather is characterized by a mild average temperature of 19°C (67°F) and can peak at a scorching 41°C (106°F), with very little precipitation, registering at only 3 mm (0.1 in) throughout the month. In contrast, February experiences much cooler temperatures, with an average of 11°C (52°F) and a minimum of -1°C (30°F), along with significantly higher precipitation levels of 133 mm (5.2 in) spread over 8 days, contributing to an increased humidity of 84%. This stark difference highlights the transition from the dry heat of early fall to the wetter and cooler conditions typical of winter. For more details, you can check out San Jose weather in February.
September and March exhibit stark contrasts in weather patterns. September enjoys warmer temperatures, with averages around 19°C (67°F) and maximums soaring up to 41°C (106°F), while March is cooler, averaging only 11°C (53°F) and peaking at 26°C (79°F). Additionally, September experiences minimal precipitation, averaging just 3 mm (0.1 in) over no rainy days, whereas March is significantly wetter, receiving 114 mm (4.5 in) of rain across 12 days. Humidity is also higher in March at 82% compared to September's 55%, highlighting the more comfortable and drier conditions of early autumn. For more detailed insights, check out San Jose weather in March.
In comparing the weather between September and April, September generally offers much warmer temperatures, with an average high of 41°C (106°F), while April sees a milder average high of 31°C (88°F). Precipitation is minimal in September, with only 3 mm (0.1 in) and no rainy days, contrasting sharply with April's wetter climate, which experiences 37 mm (1.4 in) of rain over four days. Additionally, September has a lower humidity level at 55%, whereas April's humidity is notably higher at 78%, contributing to a more humid experience during the spring month. For more detailed information, you can check San Jose weather in April.
In comparing the weather of September and May, September tends to present a warmer climate with an average temperature of 19°C (67°F) and maximums reaching up to 41°C (106°F), while May is cooler with an average of 15°C (59°F) and max temperatures of 32°C (90°F). Additionally, September is characterized by very low precipitation, recording only 3 mm over the month, and notably no rainy days, in contrast to May, which experiences around 24 mm of rain over two days. Humidity levels also differ, as September sits at a moderate 55%, while May has a higher humidity at 71%. For a more detailed look at May weather, you can check San Jose weather in May.
In comparing the weather of September and June, we find that both months exhibit relatively mild temperatures, but with some distinct differences. September features a minimum temperature of 7°C (45°F) and an average of 19°C (67°F), reaching up to 41°C (106°F) at its peak. In contrast, June starts slightly warmer with a minimum of 8°C (47°F) and averages 18°C (64°F), with a maximum temperature of 37°C (99°F). Precipitation is minimal in both months—September records just 3 mm (0.1 in) while June has a negligible 1 mm (0.0 in)—indicating dry weather throughout. Humidity levels are also noteworthy, with September averaging 55% compared to June's higher 64%, reflecting a more comfortable feel in September. For more detailed insights into the climate, check out San Jose weather in June.
In comparing the weather between September and July, both months exhibit average temperatures around 19°C (66°F), but their extremes differ significantly. September sees a remarkable maximum temperature of 41°C (106°F), contrasting with July's high of 34°C (93°F). Moreover, September experiences minimal precipitation with only 3 mm recorded, while July has no rain at all, making both months quite dry, with July maintaining slightly higher humidity at 58% compared to September's 55%. For more detailed information on July weather, check out San Jose weather in July.
September's weather sees a slight decrease in minimum temperatures compared to August, dropping from 11°C (52°F) to 7°C (45°F). However, the average temperature remains steady at 19°C (67°F) for both months. Notably, September experiences higher maximum temperatures, reaching up to 41°C (106°F) compared to August's maximum of 39°C (102°F). Both months are dry, with September receiving only 3 mm of precipitation over 0 days, while August remains completely dry with 0 mm of rain. Humidity levels are also comparable, with September at 55% and August slightly lower at 54%. For more information, you can check San Jose weather in August.
September sees a wider range of temperatures, with minimums at 7°C (45°F) and maximums peaking at a high of 41°C (106°F), while maintaining a warm average of 19°C (67°F). Notably, September experiences minimal precipitation and lower humidity levels at 55%. In contrast, October brings cooler temperatures, with minimums dropping to 5°C (42°F) and an average of 17°C (63°F), peaking at a maximum of 34°C (94°F). The month also sees a significant increase in precipitation, totaling 25 mm (1.0 in) over just one day, and humidity rises to 62%. For more details on what to expect, check out San Jose weather in October.
September typically experiences warmer temperatures compared to November, with an average of 19°C (67°F) and peak highs reaching up to 41°C (106°F). In contrast, November's average temperature drops to 13°C (56°F), with maximums around 28°C (83°F). While September boasts very little precipitation—only 3 mm over none of the month’s days—November sees a significant increase in rainfall at 56 mm over five days. Additionally, humidity levels rise from 55% in September to 78% in November, contributing to a cooler, more damp atmosphere. For more specific details on November weather, visit San Jose weather in November.
September and December in San Jose present stark contrasts in weather conditions. September typically enjoys a warm climate with average temperatures around 19°C (67°F) and occasional peaks up to 41°C (106°F), yet it experiences very little precipitation, with just 3 mm recorded over the entire month. In contrast, December sees cooler temperatures, averaging 10°C (50°F), with a maximum of 24°C (76°F) and a minimum of 1°C (34°F). This month is notably wetter, with 116 mm of rain spread over approximately nine days, contributing to higher humidity levels around 80%. For more detailed information, you can check San Jose weather in December.
As summer transitions into fall, September is marked by balmy temperatures and surprisingly dry conditions in San Jose. With average highs reaching a comfortable 19°C, this month is a welcome change from the sweltering heat often experienced in the peak of summer. Unlike other months that may bring more precipitation, September stands out with minimal rainfall, allowing residents and visitors alike to enjoy outdoor activities under mostly clear skies. The 55% humidity adds a pleasant warmth without feeling overly muggy, making it an ideal time to explore the vibrant surroundings. For more insights on what to expect throughout the year, check out San Jose Climate.