Last updated: February 24, 2025
September in San Francisco offers a pleasant mix of mild temperatures and refreshing breezes. With a maximum temperature reaching 35°C (96°F) and an average of 17°C (63°F), the month invites outdoor activities under predominantly clear skies. Temperatures can dip as low as 11°C (51°F) at night, so layers are advisable for evening outings. Remarkably low precipitation at just 2 mm (0.1 in) and no rainy days means you can enjoy sunny strolls along the picturesque waterfront. However, the humidity stays relatively high at 86%, adding a touch of warmth that enhances the vibrant atmosphere of this iconic city.
In September, San Francisco experiences a delightful shift in temperatures, with a minimum of 11°C (51°F) and an impressive maximum soaring to 35°C (96°F). This month marks a noticeable trend towards warmth, as the city's average temperature rises to 17°C (63°F). As summer draws to a close, residents and visitors alike can enjoy a blend of mild mornings and hot afternoons, making it an ideal time for outdoor activities. The contrast of cooler nights with the heat of the day perfectly encapsulates the city’s charm, creating an inviting atmosphere for exploring its iconic sights and vibrant neighborhoods.
September in San Francisco marks a notable transition in precipitation patterns as summer gives way to fall. With a mere 2 mm (0.1 in) of rainfall recorded, it reflects the tail end of the dry season, where drought-like conditions often prevail. Interestingly, September is one of the few months without any precipitation days, emphasizing the city’s typically arid climate during this time. This dry spell sets a stark contrast against the wetter months that follow, particularly October and November, when rainfall begins to pick up significantly, heralding the arrival of the rainy season. As temperatures cool, the shift in precipitation trends becomes a reminder of San Francisco's diverse climate throughout the year.
In September, San Francisco experiences an average humidity of 86%, a slight decrease from the peak levels of 87% observed in both July and August. This slight dip marks the end of the late summer months, which are characterized by higher humidity. As the city transitions into autumn, humidity levels begin to decline more noticeably, with October dropping to 80%. Throughout the year, humidity trends reveal the city’s coastal climate, where the months of winter and spring maintain relatively high humidity levels, ranging between 79% and 85%. This creates a unique atmospheric experience, making September a month where summer's warmth lingers, yet hints at the fresher conditions to come in the fall.
As September rolls into San Francisco, the UV Index remains notably high at 9, categorizing it as very high and resulting in a burn time of just 15 minutes—a trend consistent with the preceding summer months. While the UV Index begins to dip from the extreme levels observed in June and July, it still urges caution under the sun. This sustained exposure reflects a broader, seasonal pattern where spring and summer months see peak UV ratings, emphasizing the need for sun protection as you enjoy the lingering warmth of early autumn. For more detailed information and related data, check out the San Francisco UV Index.
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As September arrives in San Francisco, it ushers in a delightful continuation of summer’s warmth with an impressive 299 hours of sunshine. This vibrant month stands out as the last hurrah before autumn, seamlessly bridging the sun-drenched days of summer and the cooler months ahead. While the city basked in the most sunlight during the peak summer months of June and July, September still maintains a commendable glow, only slightly dimmer than August's 320 hours. Following the pattern of the year, the sunshine begins to wane as October approaches, hinting at the cozy days of fall. Overall, September serves as a reminder that even as the seasons shift, San Francisco's charm is ever illuminated by its golden rays.
In September, San Francisco experiences a 51% chance of sunny weather, which aligns with the city's characteristic fluctuations in sunshine throughout the year. Following the peaks of May (66%) and a slight dip in July (37%), September stabilizes to mirror the average for both October and early summer months. The transition from summer’s warmth to autumn brings a pleasantly mild climate, making it a lovely time to enjoy the outdoors. While the sunny days may not be as prevalent as earlier in the year, September’s balanced weather continues to offer plenty of opportunities for vibrant city explorations.
As summer comes to a close in San Francisco, the daylight hours gradually shift toward autumn. In September, the city enjoys a pleasant 12 hours of daylight, a gentle decrease from the peak of 14 hours in the summer months of June through August. This transition reflects the natural rhythm of the seasons, with the days becoming shorter as the year progresses. Following the bright summer days, the light begins to recede, paving the way for the cozy tones of fall. The month serves as a bridge, allowing residents to savor the lingering warmth before the daylight dips further to 11 hours in October, marking the onset of shorter, cooler days.
As September rolls in, San Francisco experiences a gentle breeze with an average wind speed of 3.3 m/s (7 mph), slightly lower than the summer months of May and June, where winds peak at 5.4 m/s (12 mph) and 4.7 m/s (10 mph), respectively. This modest decline is part of a broader trend where the winds begin to mellow after the invigorating gusts of summer. Notably, September’s wind speed aligns more closely with January's calm, hinting at the city's seasonal transition as autumn approaches. The softer breezes not only bring a change in temperature but also create a serene atmosphere, inviting residents and visitors alike to enjoy the beauty of San Francisco's iconic landscapes amidst the changing seasons.
The weather in San Francisco 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 Francisco and find detailed weather information for every month.
September presents a warm and dry climate, with average temperatures hovering around 17°C (63°F) and maximum highs reaching up to 35°C (96°F). With only 2 mm of precipitation and a humidity level of 86%, it's a month characterized by comfortable, sunny days. In stark contrast, January experiences much cooler temperatures, with an average of 11°C (52°F) and maximums peaking at 21°C (70°F). This month also sees significantly higher rainfall, totaling 106 mm (4.2 in) over approximately 9 days, while maintaining a similar humidity level of 85%. For a deeper dive into January weather specifics, you can check this link: San Francisco weather in January.
When comparing the weather in September and February, it's clear that September enjoys warmer temperatures, with a minimum of 11°C (51°F) and an average of 17°C (63°F), peaking at a maximum of 35°C (96°F). In contrast, February experiences cooler conditions, featuring a minimum of 4°C (39°F) and an average of 11°C (52°F), with peaks reaching only 20°C (69°F). Additionally, September is notably dry, receiving only 2 mm (0.1 in) of precipitation across no rainy days, while February is much wetter, recording 109 mm (4.3 in) of rain over nine days. Despite the slight difference in humidity, with September at 86% and February at 82%, the overall climate contrast highlights a significant shift from summer warmth to winter chill. For more detailed information, check out San Francisco weather in February.
September and March present contrasting weather patterns. In September, temperatures range from a mild 11°C (51°F) at night to a scorching 35°C (96°F) during the day, with an average temperature of 17°C (63°F). The month sees negligible rainfall with just 2 mm (0.1 in) and no rainy days, accompanied by high humidity at 86%. In stark contrast, March experiences cooler temperatures, with a minimum of 5°C (42°F) and a maximum of 20°C (69°F), averaging only 12°C (53°F). This month is significantly wetter, accruing 78 mm (3.1 in) of precipitation over 10 days, and slightly lower humidity at 82%. For more detailed insights, visit San Francisco weather in March.
When comparing the weather in September and April, it's clear that September tends to be warmer and drier. September boasts temperatures ranging from a minimum of 11°C (51°F) to a maximum of 35°C (96°F) with an average of 17°C (63°F) and virtually no precipitation at just 2 mm (0.1 in) over 0 days, all while maintaining a high humidity of 86%. In contrast, April experiences cooler temperatures, with a minimum of 7°C (44°F) and a maximum of 28°C (82°F), and a lower average of 13°C (55°F). Additionally, April is much wetter, receiving 35 mm (1.4 in) of rain over 5 days, alongside a more moderate humidity level of 79%. For more detailed insights, check out San Francisco weather in April.
In comparing the weather of September and May, September tends to be much warmer, with temperatures ranging from a minimum of 11°C (51°F) to a scorching maximum of 35°C (96°F). In contrast, May experiences cooler temperatures, ranging from a minimum of 8°C (47°F) to a maximum of 24°C (75°F). Additionally, September boasts significantly less precipitation, with only 2 mm (0.1 in) recorded over the month, while May sees a total of 20 mm (0.8 in) across two days of rain. Humidity levels are relatively similar, with September at 86% and May slightly lower at 83%. For more details on the weather characteristics in May, visit San Francisco weather in May.
When comparing the weather in September and June, it's evident that September generally offers warmer temperatures, with an average of 17°C (63°F) compared to June's 15°C (60°F). The maximum temperature in September can reach up to 35°C (96°F), while June peaks at 31°C (88°F). Both months experience minimal precipitation, with September receiving just 2 mm (0.1 in) and June slightly more at 3 mm (0.1 in), and both have zero days of rain. Humidity levels are relatively similar, with September at 86% and June slightly lower at 84%. For a detailed look at June's climate, you can check San Francisco weather in June.
In comparing the weather between September and July, September tends to be much warmer with average temperatures around 17°C (63°F) and a maximum of 35°C (96°F), while July sees a cooler average of 15°C (60°F) and a maximum of 24°C (76°F). Although both months experience very little precipitation—only 2 mm (0.1 in) in September and 3 mm (0.1 in) in July—September is notably drier with no rainfall days, just as July has. Humidity levels remain similar in both months, with September at 86% and July slightly higher at 87%. For a closer look at July’s weather specifics, check out this link: San Francisco weather in July.
In September, the weather shows a notable increase in temperature compared to August, with minimum temperatures remaining consistent at around 11°C (51°F) but averaging higher at 17°C (63°F) and peaking at 35°C (96°F). In contrast, August features slightly lower averages, with a maximum of 27°C (81°F). Both months experience very little precipitation, with only 2 mm (0.1 in) recorded across zero days; however, September's humidity remains slightly lower at 86%, compared to August's 87%. For more insights into the weather during this period, check out San Francisco weather in August.
In September, the weather is typically warmer, with temperatures ranging from a minimum of 11°C (51°F) to a maximum of 35°C (96°F), and an average of 17°C (63°F). The month experiences very little rainfall, with only 2 mm (0.1 in) of precipitation and no rainy days, accompanied by high humidity levels at 86%.
In contrast, October shows a noticeable drop in temperatures, with a minimum of 9°C (48°F), an average of 16°C (60°F), and a maximum of 28°C (84°F). This month brings more precipitation, measuring 30 mm (1.2 in) over two rainy days, and slightly lower humidity at 80%. For more detailed information, you can check out San Francisco weather in October.
September typically experiences warmer temperatures, with a minimum of 11°C (51°F) and a maximum reaching up to 35°C (96°F), making it one of the hotter months of the year. In contrast, November sees cooler averages, with temperatures dipping to a minimum of 6°C (43°F) and a maximum of only 23°C (74°F). While September boasts dry conditions with no recorded precipitation, November brings a significant increase in rainfall, averaging 50 mm (2.0 in) over about five days. Additionally, the humidity level is slightly higher in September at 86%, compared to 79% in November. For more detailed information, you can check out San Francisco weather in November.
In September, the weather showcases a warm and balmy atmosphere, with temperatures ranging from a minimum of 11°C (51°F) to a maximum of 35°C (96°F), while experiencing virtually no precipitation. The humidity levels are relatively high at 86%, creating a warm, sticky feel. In contrast, December brings a significant drop in temperature with a minimum of 4°C (40°F) and a maximum of 20°C (69°F). This month is notably wetter, with 95 mm (3.7 in) of precipitation spread over 9 days, and humidity levels decrease slightly to 79%. For more details about the weather in December, check out San Francisco weather in December.
In September, San Francisco often experiences a unique blend of summer warmth and coastal coolness, setting it apart from other months. With average temperatures around 17°C (63°F), the city enjoys a pleasant climate, while maximum highs can reach a sizzling 35°C (96°F). This contrasts sharply with the cooler fog-laden winds typical in spring and early summer. What's particularly notable is the lack of precipitation, with no recorded rainfall days, allowing residents and visitors to bask in the sunshine. Coupled with a high humidity level of 86%, September stands as a transitional month that still clings to summer vibes, making it an ideal time to explore the city. For a deeper understanding of what to expect year-round, check out San Francisco Climate.