Last updated: February 24, 2025
September in Chicago presents a vibrant mix of weather characteristics that define the transition from summer to fall. The month is marked by a maximum temperature reaching 32°C (90°F), with a comfortable average of 20°C (68°F) and cooler nights dipping to a minimum of 6°C (42°F). Rainfall is noticeable, with 78 mm (3.1 in) accumulating over about 9 days, contributing to a humid atmosphere, typically around 80%. This blend of warmth and moisture creates a dynamic backdrop for outdoor activities, as the city basks in the last rays of summer before autumn sets in.
As September rolls around in Chicago, the city begins to shed the sweltering heat of summer, welcoming a more temperate climate. The average temperature settles at a comfortable 20°C (68°F), with daytime highs reaching up to 32°C (90°F), making it an ideal time for outdoor activities. Nights grow cooler, dipping to a minimum of 6°C (42°F), hinting at the crispness of autumn just around the corner. This transition reflects a broader trend where temperatures gracefully spiral downward from the summer peaks, offering a perfect blend of warmth and refreshment. The early fall atmosphere invites residents and visitors alike to enjoy the stunning onset of seasonal change in the vibrant Windy City.
In September, Chicago experiences a gentle transition into fall, marked by an average precipitation of 78 mm (3.1 in) over approximately 9 days. This amount reflects a decrease from the more humid summer months, providing a welcome relief from the heavier rainfall seen in May and June. Despite being one of the drier months compared to the preceding summer, September's rainfall continues to play a critical role in preparing the city for the upcoming cooler months. As the air begins to crisp, the city's parks and landscapes come alive with vibrant autumn hues, making this month a stunning backdrop for the changing seasons, even as the precipitation begins to taper off ahead of the wetter October.
As summer transitions into fall, September in Chicago brings a slightly drier atmosphere with an average humidity of 80%. This modest decrease from the sticky summer months of July and August, both hovering around 80-81%, marks a shift that many Chicagoans eagerly anticipate. Following a pattern observed throughout the year, humidity levels tend to rise during the winter months, peaking in November at 88%. Overall, September serves as a comfortable reprieve, bridging the warm, humid days of summer with the cooler, crisper air of autumn, while maintaining a relatively consistent level of humidity that characterizes much of the city’s climate.
As September rolls into Chicago, the UV Index remains notably high, reaching 8 and categorized as very high. This trend follows a summer of extreme sun exposure, where the index peaked at 10 in both June and July. As the days grow shorter and autumn approaches, the burn time in September remains a brisk 15 minutes, emphasizing the need for sun protection even as we transition into fall. This month marks a slight decline from the blistering summer, yet it's crucial to stay vigilant, as residual intensity can still cause skin damage. For more detailed insights, check out Chicago UV Index.
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As summer gracefully transitions into fall, September in Chicago offers a splendid 288 hours of sunshine, marking a noticeable decline from the sun-drenched days of July and August. This month, while still basking in abundant daylight, sees a decrease that hints at the approaching cooler months. The sunlit hours steadily drop from the peak of 362 in July, yet September holds its own charm, outshining October's 228 hours. This trend showcases the lingering warmth of summer while gently nudging the city towards the crisp embrace of autumn, making it a delightful time for outdoor activities and exploration before the days grow shorter. Overall, September serves as a brilliant bridge between the vibrant summer and the serene fall, inviting residents and visitors alike to soak in every golden ray of sunshine.
As summer transitions into autumn, September in Chicago brings a delightful increase in sunny weather, with a substantial 56% chance of sunshine. This marks a noticeable rise from the earlier months, where chances hovered around the mid-40s. Compared to the dismal beginnings of the year, September stands out as a peak time for outdoor activities, embodying the essence of early fall with clearer skies. The trend of increasing sunshine from the typically overcast months of winter and spring illuminates a warm invitation for locals and visitors alike to savor the last bits of summer warmth before the chill of October sets in.
As September unfolds in Chicago, the days begin to shorten, offering approximately 12 hours of daylight. This marks a subtle shift from the vibrant summer months, where sunlight peaked at 15 hours in June. Following a gradual increase through spring and the peak of summer, September’s daylight diminishes slightly, hinting at the autumn transition. While days are still relatively long compared to the cold winter months ahead, the decrease nudges residents to savor the last bursts of evening light before October ushers in even shorter days. This rhythm of changing sunlight not only defines the seasons but also invites the community to embrace the unique beauty of Chicago's fall.
As September unfolds in Chicago, the city experiences a refreshing shift in wind patterns, with an average wind speed of 4.1 m/s (9 mph). This marks a subtle increase from the summer lull, where the winds dipped to their lowest at 3.0 m/s (7 mph) in August. The return of stronger breezes in September hints at the approaching autumn, contrasting with the calmer summer months. This gentle revitalization in wind speed serves as a reminder of the invigorating changes to come, bridging the gap between the warmth of summer and the crispness of fall as the city prepares for the seasonal transition ahead.
The weather in Chicago 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 Chicago and find detailed weather information for every month.
September typically boasts warmer temperatures, with an average of 20°C (68°F) and highs reaching up to 32°C (90°F). In contrast, January presents a much colder climate, with average temperatures dropping to -3°C (27°F) and highs peaking at just 14°C (57°F). While September experiences more substantial warmth and higher humidity at 80%, January is marked by extreme cold and a slightly higher humidity level of 82%. Both months see similar levels of precipitation, with September recording 78 mm (3.1 in) and January at 68 mm (2.7 in) across about nine days. For a more detailed look into January's conditions, check out Chicago weather in January.
September and February present starkly contrasting weather patterns. In September, temperatures range from a mild 6°C (42°F) at night to a warm maximum of 32°C (90°F) during the day, with an average of 20°C (68°F). This month also sees an average precipitation of 78 mm (3.1 in) over approximately 9 rainy days, accompanied by a humidity level of 80%. In stark contrast, February experiences bitterly cold temperatures, with a minimum of -30°C (-22°F) and an average temperature around -2°C (29°F). The maximum temperature reaches only 18°C (64°F). Though February has slightly less precipitation at 70 mm (2.7 in) over 12 days, it comes with higher humidity levels at 83%. To learn more about the specifics of February weather in Chicago, you can check Chicago weather in February.
In September, temperatures range from a milder minimum of 6°C (42°F) to a warm maximum of 32°C (90°F), with an average of 20°C (68°F). The month experiences significant humidity at 80% and sees around 78 mm (3.1 in) of precipitation over 9 days. In contrast, March presents a much colder climate, with temperatures ranging from a frigid minimum of -18°C (-1°F) to a maximum of 23°C (74°F) and an average of just 4°C (39°F). This month also has higher precipitation at 95 mm (3.7 in) over 11 days and slightly increased humidity at 84%. For more detailed insights into March weather in Chicago, you can check Chicago weather in March.
In comparing the weather of September and April, September offers a warmer climate with average temperatures reaching 20°C (68°F) and a maximum of 32°C (90°F), while April's temperatures are notably cooler, averaging only 8°C (47°F) with a peak of 26°C (79°F). September experiences less rainfall, with precipitation totaling 78 mm (3.1 in) over 9 days, compared to April's higher total of 125 mm (4.9 in) spread across 13 days. Additionally, September's humidity is slightly lower at 80%, compared to April's 85%, making for feelably different weather conditions. For more detailed insights, you can check Chicago weather in April.
When comparing the weather in September and May, it's clear that both months experience a range of temperatures, but they differ significantly in overall conditions. September enjoys average temperatures around 20°C (68°F), with maximum highs reaching 32°C (90°F), while May has a cooler average of 15°C (59°F), though it also reaches similar highs of 32°C (90°F). Precipitation levels are notably higher in May, with 156 mm (6.1 in) falling over 15 days, compared to September's 78 mm (3.1 in) over just 9 days. Additionally, while humidity levels remain similar, with September at 80% and May at 79%, the more frequent rainfall in May contributes to its wetter atmosphere. For more detailed insights, you can explore Chicago weather in May.
In comparing the weather of September and June, September typically experiences a more varied temperature range, with minimums dipping to 6°C (42°F) and maximums reaching up to 32°C (90°F), while June maintains a slightly higher minimum of 10°C (50°F) and a maximum of 33°C (91°F). Precipitation levels are notably higher in June, with 144 mm (5.7 in) over 13 days compared to September's 78 mm (3.1 in) across 9 days, indicating rain is more frequent in early summer. Humidity remains similar between the two months, hovering around 80% in September and slightly higher at 82% in June. For more detailed insights, you can explore Chicago weather in June.
In September, the weather begins to cool down with temperatures ranging from a minimum of 6°C (42°F) to a maximum of 32°C (90°F), averaging 20°C (68°F). In contrast, July is noticeably warmer, with minimum temperatures at 14°C (58°F) and maximums reaching 33°C (92°F), averaging 24°C (75°F). Additionally, September experiences less precipitation, totaling 78 mm (3.1 in) over 9 days, compared to July's 104 mm (4.1 in) over 12 days. Despite the varying temperatures and precipitation, both months share a similar humidity level of 80%. For more detailed information, you can visit Chicago weather in July.
September weather shows a notable decrease in minimum temperatures compared to August, with lows dropping from 11°C (53°F) to 6°C (42°F). The average temperature also dips slightly from 23°C (73°F) to 20°C (68°F), signaling the transition into cooler autumn days. While both months experience similar levels of humidity—around 80% in September and 81% in August—September sees a slight reduction in precipitation, with 78 mm (3.1 in) over 9 days compared to August’s 84 mm (3.3 in) over 11 days. For more details on August weather, you can check Chicago weather in August.
September typically brings warmer temperatures, with daily averages around 20°C (68°F) and maximums reaching up to 32°C (90°F). In contrast, October sees a notable drop in temperatures, with averages around 13°C (55°F) and minimums occasionally dipping to -1°C (31°F). While both months experience humidity levels above 80%, October tends to be wetter with increased precipitation of 142 mm (5.6 in) over 13 days, compared to September's 78 mm (3.1 in) over 9 days. For more detailed insights into October's weather, you can check out Chicago weather in October.
September and November showcase a stark contrast in weather conditions. September boasts a warm average temperature of 20°C (68°F), with highs reaching up to 32°C (90°F), while November experiences a significant drop, with an average temperature of just 4°C (40°F) and nighttime lows plummeting to -14°C (6°F). Additionally, September is generally wetter, with 78 mm (3.1 in) of precipitation over 9 days, compared to November's 65 mm (2.6 in) over 8 days. Humidity also varies slightly, beginning at 80% in September and rising to 88% by November, contributing to the chill in the air. For more detailed insights, you can check Chicago weather in November.
September and December in Chicago offer stark contrasts in weather. September enjoys warmer temperatures, with average highs reaching up to 32°C (90°F) and lows around 6°C (42°F), while December presents a much chillier climate, with average highs peaking at 18°C (64°F) and lows plummeting to -19°C (-2°F). Precipitation is slightly lower in December at 63 mm (2.5 in) over 8 days, compared to 78 mm (3.1 in) over 9 days in September. Furthermore, humidity levels are relatively high in both months, with September at 80% and December slightly higher at 84%. For a detailed look at December weather specifics, see Chicago weather in December.
As September unfolds in Chicago, the city transitions into a more moderate climate, providing a refreshing contrast to the sweltering summer months. With average temperatures hovering around a comfortable 20°C (68°F), residents experience pleasantly warm days that gradually give way to cooler evenings, making it ideal for outdoor activities. This month also marks a notable increase in moisture, as seen in the 78 mm of rainfall spread over about nine days, contributing to an atmosphere of rich humidity at around 80%. Unlike the intense heat and humidity of July and August, September's climate invites a blend of lingering warmth and crispness, heralding the approach of autumn and a vibrant change in the city's scenery. For a deeper understanding of the city's yearly climate patterns, visit Chicago Climate.