September Weather in Nantucket, United States

Last updated: February 24, 2025

In September, Nantucket experiences a delightful transition from summer to autumn, with maximum temperatures reaching up to 23°C (73°F) and a comfortable average of 19°C (66°F). As the month progresses, the minimum temperatures dip to around 13°C (56°F), marking the coolness of fall. Visitors should be prepared for moderate rainfall, with a total precipitation of 122 mm (4.8 in) spread over approximately 10 days, contributing to the island's lush landscape. The humidity level hovers around 75%, ensuring a moist but pleasant atmosphere perfect for exploring the scenic beauty of this charming destination.

September Temperature in Nantucket

As September rolls into Nantucket, temperatures begin to exhibit a gentle transition from the warmth of summer to the cooler embrace of autumn. With minimums around 13°C (56°F) and averages reaching 19°C (66°F), the island enjoys mild and pleasant days, perfect for outdoor activities. The maximum temperatures peak at 23°C (73°F), providing just enough warmth to savor the last snippets of summer. This month serves as a lovely bridge, balancing the lingering summer vibes and the impending fall chill, making it an ideal time for visitors to relish the stunning coastal scenery before the temperatures dip further.

September Weather in Nantucket: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Nantucket, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends.
JanFebMarAprMayJunJulAugSepOctNovDec373739455160676966595042
Data source: Temperature data for Nantucket generated using information from the Copernicus Climate Change Service.
Choose your preferred temperature unit
The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Nantucket

In September, Nantucket experiences a notable shift in precipitation patterns, with 122 mm (4.8 in) of rain falling over 10 days. This marks a slight increase from August, which had 98 mm (3.9 in) of precipitation across the same number of rainy days. As summer gives way to autumn, September's rainfall is a precursor to the wetter months ahead, with October typically seeing 162 mm (6.4 in). The transition highlights a trend of rising precipitation amounts as the year progresses, mirroring the region's seasonal change and signaling the approach of stormier weather in the fall.

September Precipitation Trends in Nantucket

The chart displays monthly precipitation patterns in Nantucket, with values for each month alongside September's data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September's conditions compare to those of other months.
JanFebMarAprMayJunJulAugSepOctNovDec96127114127130836498122162115132
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

September Humidity in Nantucket

As summer gives way to autumn, September in Nantucket sees a gentle decline in humidity, averaging 75%, mirroring the drier conditions of May and October. The summer months of July and August maintain a steady 76%, but the shift to fall brings a slight relief from the peak levels experienced in the winter, which hover around 84% in January and February. This transition illustrates a gradual pattern of decreasing humidity, making September a refreshing time to enjoy the island's beauty before the chill of winter sets in. Overall, Nantucket's humidity trends reveal a delightful late-summer ambiance that is both comfortable and inviting.

September Average Humidity in Nantucket

This chart illustrates the average monthly humidity levels in Nantucket, with September's data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, allowing you to see how September's humidity levels compare to other months.
JanFebMarAprMayJunJulAugSepOctNovDec84%84%82%79%75%78%76%76%76%75%80%80%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Nantucket

In September, Nantucket experiences a UV Index of 8, categorized as very high, which indicates that while summer is winding down, the sun's intensity remains significant. With a burn time of only 15 minutes, it's crucial for residents and visitors to remain vigilant about sun protection. This month follows a trend of elevated UV levels that peaked during the summer, specifically July and June, both reaching the maximum index of 10. Even as the season changes, September's UV Index highlights the need for consistent sun safety measures, making it essential to check the local forecast regularly. For more detailed information on UV trends throughout the year, visit Nantucket UV Index.

Maximum UV Index Levels in Nantucket for September

The chart shows the monthly maximum UV Index (UVI) for Nantucket in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues.
JanFebMarAprMayJunJulAugSepOctNovDec35689101098642
Data source: Nantucket September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

September Sunshine in Nantucket

As summer begins to fade, September in Nantucket still offers a generous 278 hours of sunshine, making it a delightful month for outdoor enthusiasts. While the sunlight starts to wane compared to the peak of July's 342 hours, it remains significantly brighter than the darker winter months. This gradual decline reflects the transition from vibrant summer days to the more subdued tones of autumn, yet September's weather often feels perfect for exploring the island's scenic beauty. With each day still drenched in sunlight, residents and visitors alike can enjoy plenty of opportunities for beach strolls, cycling, and savoring the local seafood scene before the colder months set in.

Monthly Sunshine Duration in Nantucket: September Highlighted

The September sunshine duration represents the total number of hours Nantucket experiences direct sunlight during the month of September, excluding cloudy or obstructed periods. This chart compares the sunshine duration of September with the other months of the year.
JanFebMarAprMayJunJulAugSepOctNovDec134h174h256h244h299h319h342h327h278h238h200h156h
Data source: Nantucket September Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Nantucket During September

September in Nantucket brings a delightful 55% chance of sunny weather, making it one of the more promising months for sunshine as summer transitions to fall. As the year unfolds, we see a trend where the likelihood of sunny days peaks during the spring and early autumn months, with March and September capturing the highest percentages. Following a series of fluctuating chances through the summer, September stands out as a notably bright time, often inviting locals and visitors alike to revel in the warmth of lingering summer rays before the cooler autumn breezes set in. This ideal balance of sunny days and mild temperatures makes September a perfect choice for outdoor activities and enjoying the picturesque beauty of Nantucket.

Percentage of Sunny Days in September in Nantucket

The chart illustrates the percentage of sunny days in Nantucket throughout the year, with September highlighted. It highlights the variation in sunshine across each month and provides an overview of the typical frequency of sunny days, offering insights into how often Nantucket experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec36%27%56%47%43%37%42%39%55%46%51%27%
Data source: Nantucket September chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Nantucket in September

As summer gently fades into autumn, September in Nantucket offers a delightful blend of warmth and shorter days, with around 12 hours of daylight marking the transition. Following the sunniest months of June and July, where daylight peaked at 15 hours, September sees a gradual decrease. This decline hints at the approach of fall, as daylight hours taper off from the 14 hours experienced in August. The month serves as a bridge, allowing residents and visitors to enjoy the lingering summer vibes while beginning to embrace the cozy charm of the upcoming season. As nature shifts gears, September stands out as a time of balance—where the golden hues of late summer meet the softer light of autumn.

Average Daylight Hours in Nantucket for September

The chart illustrates the variation in daylight duration in Nantucket throughout the year, with September highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec9h 34m10h 37m11h 58m13h 20m14h 30m15h 5m14h 46m13h 44m12h 24m11h 2m9h 50m9h 14m
Data source: Nantucket daylight hours, calculated by summing the hours between sunrise and sunset for each day.

September Winds in Nantucket

As September graces Nantucket, the winds begin to pick up slightly from the lazy days of summer, averaging 6.4 m/s (14 mph). This gentle increase signals a shift in the season, moving away from the quieter breezes of July and August, which both hovered around 5.4 m/s (12 mph) and 5.2 m/s (12 mph), respectively. Compared to earlier months, September's winds are a refreshing prelude to the fall, as they begin to mirror the more robust gusts of October at 7.3 m/s (16 mph) and November at 7.7 m/s (17 mph). This trend not only invigorates the outdoor atmosphere but also heralds the impending transition from summer’s warmth to autumn’s brisk embrace.

Average September Wind Speed in Nantucket

The chart displays monthly wind speed patterns in Nantucket, with values for each month shown alongside September's data, which is highlighted for easy comparison. It illustrates the average wind speed, offering insights into how September's wind conditions compare to the rest of the year.
JanFebMarAprMayJunJulAugSepOctNovDec8.28.07.97.56.66.55.45.26.4 m/s7.37.77.6
Data source: Nantucket September wind data, generated using information from the Copernicus Climate Change Service.

How September Weather in Nantucket Compares to Other Months

The weather in Nantucket 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 Nantucket and find detailed weather information for every month.

In September, the weather is generally mild and pleasant, with temperatures ranging from a minimum of 13°C (56°F) to a maximum of 23°C (73°F) and an average of 19°C (66°F). However, this month also sees a significant amount of precipitation, totaling 122 mm (4.8 in) over about 10 days, coupled with a humidity level of 75%. In contrast, January presents a stark change, with much colder temperatures that can drop to a minimum of -13°C (9°F) and an average of just 3°C (38°F), peaking at 13°C (55°F). Despite slightly lower precipitation of 96 mm (3.8 in), January experiences higher humidity levels at 84%, contributing to the chilly atmosphere. For more details on the January weather specifics, visit Nantucket weather in January.

September and February present stark contrasts in weather conditions. September typically enjoys milder temperatures, with averages around 19°C (66°F) and maximums reaching 23°C (73°F), while February experiences much colder weather, averaging just 3°C (38°F) and peaking at 13°C (55°F). Precipitation levels are similar, with September recording 122 mm (4.8 in) over about 10 days and February slightly higher at 127 mm (5.0 in) over 13 days, though February's humidity also rises to 84%, compared to September's 75%. For a deeper understanding of February's climate, you can check out Nantucket weather in February.

In comparing the weather of September and March, notable differences can be observed in both temperature and precipitation patterns. September enjoys milder temperatures, with a minimum of 13°C (56°F) and an average of 19°C (66°F), while March experiences much cooler conditions, with a minimum temperature of -7°C (19°F) and an average of just 4°C (39°F). While September sees an average maximum of 23°C (73°F), March peaks at only 12°C (53°F).

Precipitation is somewhat similar in both months, with September receiving 122 mm (4.8 in) over about 10 days and March closely following with 114 mm (4.5 in) spread over 11 days. Humidity levels are also higher in March at 82%, compared to 75% in September, contributing to a more damp and chilly atmosphere. For a more detailed look at March conditions, you can visit Nantucket weather in March.

When comparing the weather in September and April, a notable difference in temperature is evident. September enjoys milder conditions with an average temperature of 19°C (66°F) and maximums reaching 23°C (73°F), while April experiences cooler temperatures, averaging just 7°C (45°F) and peaking at 13°C (56°F). Both months see significant precipitation, with September averaging 122 mm over about 10 days and April slightly higher at 127 mm across 12 days. Additionally, humidity levels are relatively high in both months, with September at 75% and April increasing to 79%. For more detailed information on April weather, check out Nantucket weather in April.

When comparing the weather in September and May, September tends to be warmer, with average temperatures ranging from a minimum of 13°C (56°F) to a maximum of 23°C (73°F), while May has cooler averages with a minimum of 5°C (41°F) and a maximum of 16°C (62°F). Interestingly, both months experience a similar level of humidity at 75%, contributing to a comfortable feel despite differing temperatures. Precipitation is slightly higher in May, with 130 mm (5.1 in) over 12 days, compared to September's 122 mm (4.8 in) over 10 days. For more detailed insights, check Nantucket weather in May.

When comparing the weather in September and June, September tends to be warmer, with average temperatures reaching 19°C (66°F) compared to June's average of 15°C (60°F). September also has a higher maximum temperature of 23°C (73°F) versus June's 21°C (70°F). In terms of precipitation, September experiences more rain, totaling 122 mm (4.8 in) over 10 days, compared to June's 83 mm (3.2 in) over the same number of days. Humidity levels are slightly lower in September at 75%, while June has a humidity rate of 78%. For a closer look at the weather specifics for June, you can check Nantucket weather in June.

In comparing the weather between September and July, September tends to be slightly cooler with an average temperature of 19°C (66°F) compared to July's average of 20°C (67°F). July showcases a warmer minimum temperature of 15°C (59°F) while September starts a bit cooler at 13°C (56°F). However, September experiences significantly more precipitation, with 122 mm (4.8 in) over 10 days, contrasted with July's 64 mm (2.5 in) across 8 days. Humidity levels remain fairly comparable, with September at 75% and July slightly higher at 76%. For more insights into Nantucket's July weather, you can check this link: Nantucket weather in July.

In comparing the weather between September and August, September tends to be slightly cooler with an average temperature of 19°C (66°F), compared to August's warmer average of 21°C (70°F). The maximum temperatures are also marginally lower in September at 23°C (73°F), while August reaches up to 24°C (76°F). Interestingly, September experiences more precipitation, with 122 mm (4.8 in) over 10 days, compared to August's 98 mm (3.9 in) over 8 days. Humidity levels are quite similar, with September at 75% and August at 76%. For more details on August weather, you can check Nantucket weather in August.

September tends to be milder with average temperatures around 19°C (66°F) and maximums reaching up to 23°C (73°F). In contrast, October sees a significant drop in minimum temperatures, averaging 5°C (41°F) at night, although daytime highs can still reach 22°C (71°F). Precipitation also increases in October, with 162 mm (6.4 in) over approximately 12 days compared to 122 mm (4.8 in) in September. Both months maintain a consistent humidity level of 75%. For more detailed insights, check out Nantucket weather in October.

September and November exhibit notable differences in weather patterns. September is relatively mild, with temperatures ranging from a minimum of 13°C (56°F) to a maximum of 23°C (73°F), while the average hovers around 19°C (66°F). The month sees an average precipitation of 122 mm (4.8 in) over about 10 days, coupled with a humidity level of 75%. In contrast, November experiences much cooler temperatures, with a minimum dropping to -5°C (24°F) and a peak of 19°C (66°F), leading to an average temperature of 10°C (50°F). Although the precipitation is slightly lower at 115 mm (4.5 in) over the same number of days, humidity rises to 80%. For a closer look at what to expect in November, check out Nantucket weather in November.

September and December present stark contrasts in weather conditions. In September, temperatures range from a mild 13°C (56°F) to a maximum of 23°C (73°F), with an average of 19°C (66°F). The month typically experiences 122 mm (4.8 in) of precipitation over about 10 days, alongside a humidity level of 75%. Conversely, December brings much cooler temperatures, with a minimum of -9°C (16°F), an average of 5°C (42°F), and a maximum of 16°C (61°F). Precipitation increases slightly to 132 mm (5.2 in) over 12 days, and humidity rises to 80%. These differences make September a much warmer and more humid time compared to the chilly, wetter conditions of December. For more details, you can check Nantucket weather in December.

Compare Nantucket's Climate with Cities Worldwide

Conclusion: What to Expect From September Weather in Nantucket

As summer gracefully transitions into autumn, September on Nantucket offers a delightful shift in weather that sets it apart from the peak summer months. With average temperatures comfortably nestled around 19°C, the days are pleasantly warm yet not sweltering, allowing for enjoyable outdoor activities. The humidity tends to linger, creating a soft, refreshing atmosphere, while occasional rainfall reminds us that fall is on the horizon. Despite experiencing about 10 days of precipitation, the vibrant beauty of the island remains, as the landscape transforms into a tapestry of autumn colors. For a deeper look at how Nantucket’s weather patterns evolve throughout the year, visit Nantucket Climate.