Last updated: February 24, 2025
In September, Philadelphia experiences a vibrant transition as summer wanes, characterized by maximum temperatures soaring to 35°C (95°F) and an average hovering around 22°C (71°F). The city's weather can be quite variable, with minimum temperatures dropping to 6°C (44°F) during the month. Precipitation plays a role in this dynamic climate, with an average of 93 mm (3.7 in) falling over 10 days, contributing to a humidity level of approximately 75%. As the season shifts, residents and visitors alike can expect a mix of warm days and refreshing rains, making September a unique time to enjoy all that Philadelphia has to offer.
As September rolls into Philadelphia, temperatures begin to show a notable shift, signaling the transition from summer's swelter to the crispness of autumn. With minimums of 6°C (44°F) and averages reaching 22°C (71°F), the month offers a comfortable reprieve from the stifling heat of July and August. The maximum temperatures linger around 35°C (95°F), reminiscent of late summer, yet there's a refreshing hint of fall in the air. This balance not only invites residents outdoors but also marks the beginning of a beautiful seasonal transformation, as the city readies itself for the vibrant hues and cooler days ahead.
In September, Philadelphia experiences a moderate shift in precipitation, with around 93 mm (3.7 in) of rain falling over an average of 10 days. This represents a slight decrease from the wetter summer months of July and August, where rainfall exceeded 130 mm. While September’s precipitation is lower compared to the peak summer totals, it maintains a steady rhythm as the city transitions into fall. The milder rainfall during this month helps prepare the landscape for autumn, balancing the need for hydration while also providing respite from the heavier deluges of earlier months. As the days grow shorter and cooler, September’s forecast plays a crucial role in shaping the early fall climate of the region.
In September, Philadelphia experiences a noticeable shift in humidity levels, averaging 75%, which marks a slight increase from the summer's low of 72% in August. This transition reflects the city's gradual move away from the drier summer months, positioning humidity levels closer to the higher readings seen in early spring. Over the year, humidity in Philadelphia tends to peak during the winter, reaching a high of 84% in both January and December, while the spring months hover around the low 80s. As fall arrives, the moderate September humidity serves as a gentle reminder of the approaching cooler months, setting the stage for the wetter conditions that typically prevail in October and November.
As summer transitions to fall, September in Philadelphia sees a notable UV Index of 8, placing it in the very high exposure category. This marks a slight decline from the peak UV Index of 10 observed in the height of summer, but caution is still advised as the burn time remains a quick 15 minutes for unprotected skin. The trend throughout the warmer months highlights a consistent exposure to high UV levels, prompting residents to stay vigilant against sunburn and prolonged exposure. With the arrival of October, UV levels will continue to drop, returning to a high index of 6 and extending the burn time to 25 minutes. For more detailed information on how UV exposure varies throughout the year, visit Philadelphia UV Index.
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As summer gracefully transitions into autumn, September in Philadelphia boasts a delightful 264 hours of sunshine, continuing the trend of ample daylight from the warmer months. Following the sun-drenched heights of July and June, which recorded 346 and 311 hours respectively, September maintains a generous amount of sunlight, although it marks a shift towards shorter days. This month balances the lingering warmth of summer with the crisp approach of fall, heralding a time when residents can savor the sun’s rays before autumn's cooler embrace takes hold. The gradual decline in sunshine hours is a gentle reminder of the seasonal rhythm, as October echoes this trend with 223 hours. Overall, September serves as a golden bridge between the vibrancy of summer and the cozy charm of fall.
In September, Philadelphia experiences a notable uptick in sunny weather, with a chance of sunshine rising to 52%. This trend marks a significant improvement from the summer months of June and August, which see lower probabilities of sun at 36% and 33%, respectively. Comparatively, the chances of sunny days in September are more favorable than the surrounding months, like October, which dips to 38%. As summer gives way to fall, residents and visitors alike can enjoy a higher likelihood of clear skies and pleasant weather, making September an appealing time to explore the city outdoors.
In Philadelphia during September, daylight begins to wane as summer approaches its end, offering around 12 hours of sunlight. This marks a gradual transition from the longer, sun-drenched days of summer, where June and July bask in a maximum of 14 hours of daylight. The daylight hours then start to decline steadily, with September seeing a slight dip compared to the earlier months. This shift sets the stage for autumn, where sunlight drops further to 11 hours in October and levels off to 9 hours in the winter months. Observing this trend, we see a natural rhythm of increasing and decreasing daylight that beautifully encapsulates the changing seasons in this vibrant city.
As autumn begins to whisper through the streets of Philadelphia in September, the average wind speed picks up to 3.0 m/s (7 mph), a gentle yet noticeable breeze that signals the transition from summer's swelter to cooler days ahead. This slight uptick from the languid summer months, where winds dipped to a minimum of 2.2 m/s (5 mph) in August, creates a refreshing ambiance as locals start to embrace fall activities. Interestingly, the wind speed remains constant into October, highlighting a consistent early autumn atmosphere. Compared to the early months of the year, where wind speeds hovered around 3.3 to 3.7 m/s, September's winds offer a pleasant, mild shift, encouraging leisurely strolls through the city's vibrant parks as leaves begin to turn. Overall, the winds in September reflect a balance, providing just enough movement to herald the seasonal change without overwhelming the senses.
The weather in Philadelphia 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 Philadelphia and find detailed weather information for every month.
September weather is characterized by warm temperatures, with averages around 22°C (71°F) and highs reaching up to 35°C (95°F), making it a month filled with summer-like warmth. In contrast, January brings a much chillier atmosphere, with average temperatures dropping to around 2°C (36°F) and nightly lows plummeting to -17°C (1°F). While September experiences more precipitation with 93 mm (3.7 in) over approximately 10 days, January sees less rainfall at 63 mm (2.5 in) over 9 days, but its higher humidity at 84% can contribute to a damp, chilly feel. For more detailed insights, check out Philadelphia weather in January.
September and February showcase stark contrasts in weather patterns. September typically boasts mild to warm temperatures, ranging from a minimum of 6°C (44°F) to a maximum of 35°C (95°F), with an average of 22°C (71°F). While it experiences relatively high humidity at 75% and about 93 mm (3.7 in) of rainfall over 10 days, the overall climate is generally more temperate and pleasant. In contrast, February is considerably colder, with temperatures dipping as low as -15°C (5°F), averaging only 4°C (39°F) and reaching a maximum of 26°C (78°F). The month receives slightly more precipitation, totaling 108 mm (4.3 in) over 11 days, and higher humidity at 83%. For more details on February's climate, visit Philadelphia weather in February.
When comparing the weather in September and March, significant differences emerge. September typically boasts warmer temperatures, with averages around 22°C (71°F) and highs reaching up to 35°C (95°F), making it a comfortable month for outdoor activities. In contrast, March experiences much cooler conditions, with average temperatures of only 7°C (44°F) and minimums dropping to -11°C (12°F). Precipitation levels are relatively close, with September receiving 93 mm (3.7 in) and March slightly higher at 107 mm (4.2 in), both spread across about 10 rainy days. Additionally, March tends to have higher humidity at 83% compared to September's 75%. For more detailed insights on March weather specifically in Philadelphia, you can check Philadelphia weather in March.
When comparing the weather in September and April, we see notable differences in temperature and precipitation patterns. September tends to be warmer, with average temperatures around 22°C (71°F) and highs reaching up to 35°C (95°F), while April features cooler temperatures, averaging 12°C (55°F) and dipping down to a minimum of -2°C (29°F). In terms of precipitation, April experiences slightly more rainfall, totaling 105 mm (4.1 in) over 11 days compared to September's 93 mm (3.7 in) over 10 days. Additionally, April has a higher humidity level at 81%, whereas September's humidity is around 75%. For a more detailed look at April's weather, check out Philadelphia weather in April.
When comparing the weather in September and May, both months can reach a maximum temperature of 35°C (95°F), but they showcase distinct differences overall. September tends to have a higher average temperature of 22°C (71°F), while May averages at 18°C (65°F). In terms of precipitation, May is wetter with 133 mm (5.2 in) of rain over 14 days, compared to September's 93 mm (3.7 in) spread across 10 days. Humidity levels are also slightly elevated in May at 78%, compared to September's 75%. For more detailed insights, you can check Philadelphia weather in May.
When comparing the weather in September and June, we notice some interesting differences. In June, temperatures range from a minimum of 10°C (50°F) to a maximum of 36°C (98°F), with an average temperature of 23°C (74°F). This month experiences slightly higher humidity at 79% and just a bit more precipitation, totaling 102 mm (4.0 in) over 11 days. In contrast, September features a broader temperature range, with a minimum of 6°C (44°F) and a maximum of 35°C (95°F), while maintaining an average of 22°C (71°F). Although it has slightly less precipitation at 93 mm (3.7 in) over 10 days, the humidity is relatively close at 75%. For a more detailed look into June’s weather, check out Philadelphia weather in June.
When comparing the weather in July and September, notable differences emerge. July typically experiences warmer temperatures, with minimums around 14°C (58°F) and averages reaching 26°C (79°F), while September's temperatures start lower, ranging from a minimum of 6°C (44°F) to an average of 22°C (71°F). Additionally, July can reach higher maximum temperatures, peaking at 37°C (99°F), compared to September's maximum of 35°C (95°F). Precipitation is also higher in July at 131 mm (5.2 in) over 13 days, while September sees 93 mm (3.7 in) spread across 10 days. Humidity levels remain relatively similar, with July at 74% and September slightly higher at 75%. For more detailed daily weather patterns, you can check Philadelphia weather in July.
When comparing the weather between September and August, we see notable differences. September experiences a wider temperature range, with a minimum of 6°C (44°F) compared to August's warmer minimum of 14°C (58°F), while both months share a maximum of 35°C (95°F for September and 96°F for August). The average temperature in September is slightly lower at 22°C (71°F), in contrast to August's 25°C (77°F). Precipitation also decreases in September, with 93 mm (3.7 in) falling over 10 days, compared to 134 mm (5.3 in) over 14 days in August. Humidity remains relatively consistent but is slightly higher in September at 75% versus 72% in August. For more detailed information, check out Philadelphia weather in August.
In September, temperatures range from a cool minimum of 6°C (44°F) to a warm maximum of 35°C (95°F), with an average temperature of 22°C (71°F). The month experiences moderate precipitation, totaling 93 mm (3.7 in) over 10 days, accompanied by a humidity level of 75%.
In contrast, October sees a drop in average temperatures, with a minimum of 2°C (37°F) and an average of 16°C (61°F), although the maximum can still reach 35°C (96°F). Precipitation increases slightly to 106 mm (4.2 in) over 9 days, while humidity rises to 81%. For more detailed information, you can check Philadelphia weather in October.
In September, the weather typically features a wide range of temperatures, with minimums around 6°C (44°F) and maximums soaring up to 35°C (95°F), leading to an average temperature of 22°C (71°F). The month sees about 93 mm (3.7 in) of precipitation over 10 days, accompanied by a humidity level of 75%. In contrast, November brings a notable shift, with temperatures dropping significantly to a minimum of -8°C (18°F) and an average of just 8°C (47°F), while the maximum reaches 25°C (77°F). Precipitation during this month is slightly lower at 83 mm (3.3 in) over 8 days, but the humidity rises to 85%. For more insights on the weather in November, you can visit Philadelphia weather in November.
September and December present contrasting weather patterns. In September, the temperatures range from a mild 6°C (44°F) at night to a warm 35°C (95°F) during the day, with an average of 22°C (71°F). The month experiences a total precipitation of 93 mm (3.7 in) over about 10 days, accompanied by a humidity level of 75%. In stark contrast, December sees much colder temperatures, with lows plummeting to -12°C (10°F) and daily highs reaching only 19°C (67°F), averaging around 4°C (40°F). Precipitation slightly increases to 100 mm (4.0 in), with the same frequency of rainfall spread across 10 days, but humidity rises to 84%. For more details, you can check Philadelphia weather in December.
As September unfolds in Philadelphia, it marks a transition from the sweltering heat of summer to the cooler embrace of fall. With average temperatures hovering around a comfortable 22°C (71°F), this month offers a pleasant respite from the peak summer days, where highs can soar up to 35°C (95°F). Despite the warmth, September is also characterized by increased humidity at 75%, and a notable amount of precipitation, totaling 93 mm (3.7 in) across approximately 10 days. This unique blend of warmth and moisture sets a different tone compared to the drier and cooler months ahead, making September a vibrant time for outdoor activities and enjoying the city's rich seasonal offerings. For more insights into how the weather shapes the city's atmosphere, check out Philadelphia Climate.