Last updated: February 24, 2025
September in Boston showcases a dynamic climate as summer transitions into fall. The month experiences maximum temperatures soaring to 31°C (89°F) while the average hovers around 18°C (64°F), providing a comfortable backdrop for outdoor activities. However, the temperature can dip as low as 3°C (38°F), especially towards the end of the month. Rainfall is not uncommon, with 76 mm (3.0 in) of precipitation spread over 9 days, contributing to a humidity level of 76% that often envelops the city. Whether you're exploring the vibrant streets or enjoying a picturesque view of the Charles River, September's varied weather adds to Boston's charm.
In September, Boston experiences a delightful transition as summer begins to wane, characterized by pleasant temperatures that hint at the approaching fall. The average temperature hovers around 18°C (64°F), with a minimum of 3°C (38°F) and a maximum reaching up to 31°C (89°F). This month strikes a perfect balance, as lingering warmth from summer still embraces the city, while cooler evenings signal the onset of autumn. Compared to the peak of summer, where July and August showcase higher averages of 22°C (72°F) and 21°C (70°F), September offers a gentle reprieve, making outdoor activities especially enjoyable. As the leaves begin to change, locals and visitors alike can relish in the mild climate that makes Boston's September a truly enchanting time of year.
In September, Boston experiences a notable dip in precipitation, receiving 76 mm (3.0 in) of rain across just 9 days. This marks the month as one of the driest in the latter part of the year, with rainfall reducing compared to the more torrential summer months, particularly July, which often sees the highest levels of precipitation at 127 mm (5.0 in). As the city transitions into fall, the decline in both the amount and frequency of rain suggests a shift towards a drier climate ahead, setting the stage for October's upcoming precipitation surge, which averages 134 mm (5.3 in) over 16 days. This pattern highlights September as a transitional month, bridging the wetter summer and fall seasons, with a pleasant balance for both residents and visitors to enjoy the lingering warmth of late summer while still experiencing the charm of early autumn.
In September, Boston experiences a slight uptick in humidity, with levels averaging 76%. This marks a gradual decline from the summer months, where humidity peaked at 77% in July and dropped to 72% in August. As the city transitions into autumn, September acts as a bridge, allowing for a subtle reintroduction of moisture into the air. This trend reflects an overall pattern where humidity levels begin to creep back up in the fall, following the drier summer months, and signals the return of more comfortable, yet still moderately humid conditions that pave the way for cooler October days.
As summer transitions into fall, Boston experiences a notable shift in UV exposure. In September, the UV Index stands at 8, categorized as very high, indicating that sun protection remains essential. This marks a gradual decline from the peak summer months, where readings reached a maximum of 10 in both June and July. Interestingly, although September's UV levels are lower than the peak summer indices, they still necessitate caution, with a burn time of just 15 minutes. As the days shorten and temperatures cool, it's a reminder that harmful UV rays are still prevalent, emphasizing the importance of sun safety as we move towards cooler months. For more information about UV levels throughout the year, visit Boston UV Index.
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September in Boston marks a delightful transition, boasting 293 hours of sunshine that gently winds down the summer glow. Following the sun-drenched months of July and August, both recording an impressive 338 hours, September offers a more moderate yet still vibrant display of light as the days begin to shorten. The month showcases a distinct trend, where the exuberance of summer lingers just a bit longer, inviting residents and visitors alike to revel in the crisp air and hint of autumn. This gradual decrease from the peak summer brightness sets the stage for the cooler months ahead, yet the golden rays of September continue to entice, highlighting the beauty of the city's transition into fall.
As September approaches in Boston, the likelihood of enjoying sunny weather remains quite promising, with a 41% chance of sun. This positions September as a time of mild transition, where sunshine is often accompanied by the lingering warmth of summer. Compared to the earlier months, the probability for sunny days drops slightly from the peak of 45% in June, yet it is relatively stable compared to the fluctuating chances seen from January through August. This trend highlights September as a favorable month for outdoor activities, as residents can still bask in some sun before the autumn chill sets in, making it a delightful time to appreciate the beauty of the changing seasons.
In September, Boston enjoys a delightful transition into autumn, with 12 hours of daylight illuminating the crisp, early fall days. As summer fades, the daylight gradually decreases from a peak of 15 hours in June to the 14 hours seen in July and 13 hours in August. This decline ushers in a season where shorter days make cozy gatherings and vibrant foliage all the more appealing. As the month unfolds, daylight dwindles, hinting at the approaching 10 hours of October. The steady ebb of daylight from spring to fall paints a beautiful picture of seasonal change, where each hour of sunshine becomes a treasured part of the day.
As September arrives in Boston, the average wind speed settles at a brisk 3.5 m/s (8 mph), reminiscent of the early spring breezes. This month marks a return to the moderate winds experienced earlier in the year, reflecting a slight uptick from the languid summer days, where gusts dropped to a gentle 2.7 m/s (6 mph) in August. The winds in September offer a refreshing contrast to the humidity of summer, hinting at the approaching autumn. Notably, October doesn't stray far from this trend, maintaining a similar wind speed, which suggests that Boston's fall will continue to bring a lively atmosphere, animated by the invigorating winds that sweep through the city. Overall, September serves as a transitional phase, balancing the lighter breezes of summer with the steadily increasing gusts that characterize the later months, paving the way for the more pronounced winds of fall and winter.
The weather in Boston 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 Boston and find detailed weather information for every month.
In comparing the weather of September and January, one can see a stark contrast in temperatures and conditions. September boasts a much warmer climate with an average temperature of 18°C (64°F), peaking at a comfortable 31°C (89°F), while January experiences frigid temperatures, with averages around -3°C (27°F) and extreme lows dropping to -21°C (-6°F). Additionally, September has a relatively moderate level of precipitation at 76 mm (3.0 in) over 9 days, whereas January sees increased precipitation at 87 mm (3.4 in) spread over 14 days, coupled with higher humidity levels of 91%. For more insights, you can check Boston weather in January.
In September, the weather tends to be much milder, with temperatures ranging from a minimum of 3°C (38°F) to a maximum of 31°C (89°F) and an average of 18°C (64°F). The month experiences around 76 mm (3.0 in) of precipitation over about 9 days, with a humidity level of 76%. In contrast, February presents a starkly different climate characterized by much colder conditions. Temperatures can plummet to as low as -19°C (-2°F), with an average of -2°C (29°F) and a maximum of 20°C (69°F). February sees slightly higher precipitation at about 90 mm (3.5 in), but spread over more days—approximately 16 days—resulting in a humidity level of 91%. For a deeper look into the cold conditions, check out Boston weather in February.
In comparing the weather of September and March, we see a notable shift in temperatures and conditions. September boasts a more temperate climate with minimums of 3°C (38°F) and averages around 18°C (64°F), allowing for warmer days with highs reaching up to 31°C (89°F). In contrast, March introduces much colder weather, with minimum temperatures dropping as low as -18°C (0°F) and an average just above freezing at 2°C (35°F). Despite relatively similar precipitation levels—76 mm (3.0 in) in September compared to 80 mm (3.2 in) in March—the distribution of rainy days differs, with March experiencing precipitation over 13 days. Additionally, March shows higher humidity levels at 88% compared to September's 76%. For more details on the weather trends during this month, you can check Boston weather in March.
September and April exhibit notable differences in weather patterns. September typically enjoys milder temperatures, with averages around 18°C (64°F) and highs reaching up to 31°C (89°F). In contrast, April is cooler on average at 7°C (45°F), with nights experiencing lows as chilly as -5°C (23°F). Precipitation also varies, with September receiving around 76 mm (3.0 in) over about 9 days, while April sees a higher total of 119 mm (4.7 in) but stretched over 15 days. Additionally, the humidity is noticeably higher in April at 88%, compared to September's 76%. For a more detailed look at April weather, check out Boston weather in April.
September and May present different weather patterns that influence the overall climate experience. In September, temperatures range from a minimum of 3°C (38°F) to a maximum of 31°C (89°F), with an average temperature of 18°C (64°F). The month sees 76 mm (3.0 in) of precipitation over about 9 days and a humidity level of 76%. In contrast, May features cooler temperatures, with a minimum of -2°C (29°F) and an average of 14°C (58°F), peaking at 32°C (89°F). This month is also wetter, receiving 107 mm (4.2 in) of precipitation across 14 days and slightly higher humidity at 82%. For more specific details, you can explore Boston weather in May.
In comparing the weather of September and June, both months exhibit warm temperatures, but September tends to have slightly cooler averages. September's minimum temperature is 3°C (38°F), with an average of 18°C (64°F) and a maximum of 31°C (89°F), while June starts at a minimum of 5°C (42°F) and reaches an average of 19°C (67°F) and a peak of 32°C (90°F). Precipitation is also a factor, with September receiving 76 mm (3.0 in) over 9 days compared to June's 89 mm (3.5 in) over 12 days. Additionally, humidity levels are very similar, with September at 76% and June slightly higher at 79%. For more detailed insights into June weather, visit Boston weather in June.
In comparing the weather between September and July, there are notable differences in temperature and precipitation patterns. September boasts a wider temperature range, with minimums dropping to 3°C (38°F) and maximums reaching 31°C (89°F), averaging around 18°C (64°F). In contrast, July experiences a milder minimum of 11°C (52°F) and maximums of 33°C (91°F), averaging 22°C (72°F). Additionally, September sees less rainfall, with 76 mm (3.0 in) of precipitation over 9 days, compared to July's 127 mm (5.0 in) over 15 days. Despite the slight difference in humidity levels, with September at 76% and July at 77%, the overall weather in September tends to be drier and cooler. For more details on July weather, you can visit Boston weather in July.
In comparing the weather between September and August, we notice some distinct shifts. September experiences a broader temperature range, with minimums dropping to 3°C (38°F) compared to August's milder 8°C (47°F). While both months feature similar maximum temperatures peaking at around 31°C (89°F for September and 88°F for August), September averages a cooler 18°C (64°F) versus August's warmer 21°C (70°F). Precipitation levels also differ slightly, with September receiving 76 mm over 9 days, while August has a bit more, at 85 mm across 13 days. Interestingly, September's humidity is slightly higher at 76%, compared to August's 72%. For more detailed insights into August's climate, you can check Boston weather in August.
September typically sees milder temperatures with an average of 18°C (64°F), ranging from a low of 3°C (38°F) to a high of 31°C (89°F). The month experiences a moderate amount of precipitation, totaling 76 mm (3.0 in) over about 9 days, with humidity levels at 76%. In contrast, October brings cooler temperatures, with an average of 12°C (54°F) and a more significant dip in the lows, hitting 0°C (32°F) while peaking at a comfortable 29°C (84°F). The increase in rainfall is notable, with October recording 134 mm (5.3 in) over 16 days and higher humidity at 83%. For more details, you can check Boston weather in October.
In September, the weather is considerably warmer, with average temperatures ranging from a mild 18°C (64°F) to a high of 31°C (89°F), punctuated by relatively lower humidity levels around 76%. Rainfall is moderate, totaling 76 mm (3.0 in) over about 9 days. In contrast, November sees a sharp drop in temperatures, with an average of 4°C (40°F) and minimums dipping as low as -14°C (8°F). The month is also wetter, with 99 mm (3.9 in) of precipitation spread across 15 days and higher humidity at 88%. For more details on how November weather impacts daily life, check out Boston weather in November.
September and December present strikingly different weather conditions. In September, temperatures range from a mild 3°C (38°F) at night to a warm 31°C (89°F) during the day, averaging around 18°C (64°F). Precipitation is moderate, totaling 76 mm (3.0 in) over about 9 days, with humidity at 76%. In contrast, December experiences colder temperatures, with lows plummeting to -19°C (-2°F) and a much cooler average of 0°C (33°F), peaking at 18°C (65°F). Rainfall increases, accumulating 105 mm (4.1 in) across 18 days, accompanied by higher humidity at 87%. For a detailed look at Boston's weather in December, visit Boston weather in December.
As summer fades into autumn, September in Boston offers a delightful transition characterized by mild temperatures and increased humidity. With average highs around 18°C, the city enjoys a pleasant warmth, though occasional spikes can reach up to 31°C, reminding us of the lingering heat from summer. However, the month is also known for its intermittent rainfall, with about nine days experiencing precipitation, totaling around 76 mm. This balance of warmth and moisture contributes to a unique ambiance that sets September apart from both the sweltering summer and the crisp fall months. For a deeper understanding of Boston's weather patterns throughout the year, explore Boston Climate.