Last updated: February 24, 2025
September in Pasadena, United States, is characterized by warm temperatures and dry conditions. The month sees maximum temperatures soaring up to 44°C (112°F), while the average hovers around a comfortable 23°C (74°F). Nights cool down to a pleasant 10°C (51°F). Remarkably, rainfall is sparse, with only 4 mm (0.1 in) recorded and no precipitation days, resulting in a humidity level of 48% that contributes to the dry heat. This combination makes September a quintessential Southern California month, perfect for outdoor activities amidst the lingering warmth of summer.
In September, Pasadena experiences a noticeable transition in temperatures, with minimums averaging 10°C (51°F) and maximums soaring to a scorching 44°C (112°F). This month marks a peak in heat, showcasing a dramatic rise compared to the previous months, particularly July and August, which also featured high temperatures but slightly less extreme. The average temperature settles at a comfortable 23°C (74°F), making it a time where warm days gradually hint at the coolness of autumn ahead. Overall, September serves as a bridge from the summer swelter to the milder days of fall, inviting both locals and visitors to embrace the lingering sunshine while preparing for the seasonal shift.
In September, Pasadena experiences a nearly dry spell, accumulating only 4 mm (0.1 in) of rain across the month, yet remarkably, it registers no precipitation days. This pattern exemplifies the area's transition into fall, following a notably arid summer characterized by mere drizzles in the preceding months of July and August. The stark contrast to the wetter months, like March and January, highlights the region's seasonal variability. As October approaches, precipitation begins to pick up slightly, but the overall trend showcases Pasadena's characteristic sunny skies and dryness during this time of the year, setting the stage for the lush, rainier months that follow later in the fall and winter.
In Pasadena, United States, September ushers in a noticeable shift in humidity, with levels rising to 48% after the drier summer months. This increase represents a slight uptick following August's low of 39%, marking a gradual transition away from the dry heat. As the year progresses, humidity steadily climbs back towards the winter averages, beginning its ascent from the summertime lows of 46% in July and 52% in June. Compared to the higher humidity levels experienced in the earlier months—peaking at 82% in February—September's figures indicate a refreshing change as the city gears up for the fall, where atmospheric moisture begins to return.
In September, Pasadena experiences a very high UV Index of 10, indicating a significant risk of harm from unprotected sun exposure, with a burn time of just 15 minutes. This month maintains the intense trend established during the summer, as the UV Index has been exceptionally high from May through August with peak levels reaching 12 in July. As the season transitions into autumn, a slight decrease occurs, yet the UV radiation remains potent, reminding residents to take necessary precautions. For more details on the UV Index trends throughout the year, you can visit the Pasadena UV Index.
UV Risk Categories
September in Pasadena brings a delightful transition as summer's warmth lingers with an impressive 315 hours of sunshine. This marks a slight decline from the sun-drenched peak of July at 381 hours, yet it still outshines the earlier months, creating a perfect backdrop for outdoor activities and community events. As the year progresses, September stands as a bridge, gently ushering in fall while holding onto the vibrancy of summer. With daylight hours gradually diminishing toward October's 292 hours, residents and visitors alike can relish the golden sunsets and vibrant atmospheres that define this charming California city during its sunny September.
In Pasadena, September boasts an impressive 85% chance of sunny weather, making it one of the brightest months of the year. This trend of increasing sunshine is evident as summer unfolds, with August leading at 82%, and September surpassing it as the sun shines more consistently. The overall trend from the beginning of the year shows a steady rise in sunny days, peaking in the late summer and early fall. Following the warm, sun-drenched months of June and July, September continues to deliver delightful weather before the cooler fall season sets in, ensuring that residents and visitors alike can enjoy outdoor activities under clear blue skies.
As summer transitions into autumn, September in Pasadena, United States, offers a delightful blend of lingering warmth and shorter days, with approximately 12 hours of daylight. This reduction follows the peak summer months of June and July, which boast up to 14 hours of sunlight. The daylight duration gradually decreases throughout the fall, paralleling the cooling temperatures. Interestingly, September's light hours serve as a gentle reminder of the impending autumn, leading seamlessly into the 11 hours expected in October, and eventually culminating in the shorter days of winter. Overall, Pasadena experiences a subtle yet captivating shift in daylight that enhances the seasonal charm of the region.
As summer fades into autumn, September in Pasadena experiences a gentle shift in its breezy demeanor, marked by an average wind speed of 1.7 m/s (4 mph). This slight decline continues the trend observed since May, where wind speeds gradually decreased from 1.9 m/s to their September low. The consistent calm, characterized by softer gusts throughout the summer months, sets the stage for a more tranquil transition into the fall season. Interestingly, September's breeziness remains higher than the winter months of January through April, which boast speeds around 2.1 m/s (5 mph). Overall, the winds weave a subtle narrative of seasonal change, inviting the lush autumn colors with a soft whisper as summer gives way to fall.
The weather in Pasadena 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 Pasadena and find detailed weather information for every month.
September and January present a stark contrast in weather conditions. In September, temperatures soar, with an average high of 23°C (74°F) and peaks reaching an impressive 44°C (112°F), while the month sees minimal precipitation, averaging just 4 mm (0.1 in) and experiencing no rain days at all. The humidity sits at a comfortable 48%, making it a hot, dry month.
In contrast, January offers cooler temperatures, with an average low of 0°C (32°F) and an afternoon peak of 29°C (84°F). This month is marked by a significant increase in rainfall, totaling 75 mm (3.0 in) over about 5 days, leading to a much higher humidity level of 78%. Those interested in a deeper look into January’s weather can explore more details through this link: Pasadena weather in January.
September and February offer stark contrasts in weather. In September, temperatures can reach a scorching maximum of 44°C (112°F), with an average of 23°C (74°F) and minimal precipitation of just 4 mm (0.1 in) over no rainy days, resulting in a relatively dry atmosphere with 48% humidity. In contrast, February features cooler temperatures, with highs of 28°C (83°F) and an average of 12°C (54°F). This month sees increased precipitation at 65 mm (2.6 in) over six days, leading to a much more humid environment at 82%. For a detailed comparison of conditions, you can refer to Pasadena weather in February.
September and March present contrasting climatic characteristics. In September, temperatures soar with a minimum of 10°C (51°F) and an average of 23°C (74°F), peaking at a scorching 44°C (112°F). This month is characterized by minimal precipitation, with just 4 mm (0.1 in) and no rainy days, resulting in a relatively low humidity of 48%. In stark contrast, March experiences cooler weather with a minimum of 1°C (34°F) and an average of 13°C (56°F), reaching a maximum of 30°C (86°F). This month is much wetter, featuring 85 mm (3.4 in) of precipitation over 10 days, contributing to a higher humidity of 75%. For a detailed look at the specific weather patterns during March, you can explore Pasadena weather in March.
In September, the weather tends to be hotter, with average temperatures around 23°C (74°F) and maximums soaring up to 44°C (112°F). The month is typically dry, with only 4 mm of precipitation recorded and no rainy days, resulting in a relatively low humidity of 48%. In contrast, April offers cooler temperatures, with a minimum of 6°C (43°F) and an average of 17°C (62°F). This month sees a bit more precipitation, totaling 22 mm (0.9 in) over two days, and a higher humidity level of 68%. For further insights into spring weather conditions, you can check Pasadena weather in April.
September and May showcase distinct weather patterns, with September typically presenting warmer temperatures. In September, the average temperature is 23°C (74°F), with highs reaching up to 44°C (112°F), while May offers a cooler average of 18°C (64°F) and a maximum of 34°C (94°F). Additionally, September is quite dry, experiencing no precipitation, whereas May sees a bit more rain, averaging 16 mm (0.6 in) over three days. Humidity levels are also higher in May at 57%, compared to 48% in September. For more detailed insights, check out Pasadena weather in May.
In comparing the weather between September and June, we find that both months exhibit relatively warm temperatures, with September having a minimum of 10°C (51°F) and an average of 23°C (74°F), while June sees a minimum of 11°C (51°F) and a slightly lower average of 22°C (71°F). The maximum temperatures in September can reach up to 44°C (112°F), which is notably higher than June's peak of 40°C (105°F). Precipitation levels are quite low in both months, with September recording only 4 mm (0.1 in) and June slightly lower at 1 mm (0.1 in), and both months experience no rainy days. Humidity is marginally higher in June at 52%, compared to 48% in September. For more detailed information, you can refer to Pasadena weather in June.
In comparing the weather between September and July, September boasts a slightly lower average temperature of 23°C (74°F), compared to July's warmer 25°C (77°F). Both months experience minimal precipitation, with September recording only 4 mm and July at 2 mm, and neither month reporting any rainy days. Additionally, September features a marginally cooler minimum temperature of 10°C (51°F), while July starts off warmer at 13°C (57°F). Humidity levels are quite similar, with September at 48% and July at 46%. For a more in-depth look at July’s weather specifics, you can visit Pasadena weather in July.
In comparing the weather between August and September, we see a noticeable shift. September offers a broader temperature range, with a minimum of 10°C (51°F) and a maximum that can reach as high as 44°C (112°F), while August maintains slightly milder temperatures, ranging from a minimum of 15°C (59°F) to a maximum of 40°C (105°F). Both months exhibit minimal precipitation, with September recording 4 mm and August just 2 mm, and neither experiencing any rain days. Interestingly, September also has higher humidity at 48%, compared to August's 39%. For more details on August weather patterns, you can check out Pasadena weather in August.
In September, the weather tends to be warmer, with average temperatures around 23°C (74°F) and maximum highs reaching up to 44°C (112°F). The month is relatively dry, with no recorded precipitation and humidity at 48%. In contrast, October experiences cooler temperatures, with averages dropping to 20°C (68°F) and highs peaking at 38°C (101°F). This month also sees a slight increase in humidity to 59% and some precipitation, totaling 9 mm over just one day. For more detailed information on October weather, you can check Pasadena weather in October.
September and November present a stark contrast in weather conditions. In September, temperatures can soar with a minimum of 10°C (51°F), averaging 23°C (74°F), and reaching a maximum of 44°C (112°F), while experiencing extremely low precipitation at just 4 mm and no rainy days, resulting in a relatively dry atmosphere with 48% humidity. In contrast, November brings cooler temperatures with a minimum of 2°C (37°F) and an average of 16°C (61°F), peaking at 31°C (89°F). The month is markedly wetter, with 24 mm of precipitation over two days and a higher humidity level of 72%. For more details about Pasadena’s weather in November, you can visit Pasadena weather in November.
In September, the weather tends to be quite warm, with average temperatures reaching up to 23°C (74°F) and maximums soaring as high as 44°C (112°F). This month is characterized by dry conditions, with minimal precipitation and low humidity at 48%. In contrast, December brings a significant drop in temperatures, averaging around 12°C (53°F) and peaking at 27°C (81°F). Furthermore, December experiences increased precipitation, totaling 77 mm (3.1 in) over five days, and humidity rises to 76%. For a more detailed look at the December climate, you can check Pasadena weather in December.
As summer transitions to fall, September in Pasadena presents a unique blend of warmth and dryness, distinguishing it from the cooler months that follow. With average temperatures hovering around 23°C (74°F) and maximums occasionally soaring to 44°C (112°F), this month offers a lingering taste of summer. Notably, precipitation is minimal, with no rainy days recorded, allowing residents and visitors to enjoy the typically low humidity of 48%. This dry and moderately warm climate sets the perfect backdrop for outdoor activities, making September a delightful time to experience everything Pasadena has to offer. For a deeper insight into the weather patterns of Pasadena, check out Pasadena Climate.