Nantucket weather in September
Temperature, sea and sunshine in September: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in September
Poor
Best time to visit: July – August
What is the weather like in Nantucket in September?
In September, Nantucket is mild: daytime highs average 19 °C, and nights cool down to about 17 °C. The sea averages 18.8 °C – bracing, so a wetsuit helps for longer swims. The sun shines for around 7 hours a day. Rain falls on about 8 days, adding up to 104 mm. It is often windy, with gusts of around 30 km/h. All in all, September is not an ideal month for a holiday in Nantucket.
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 52 | 32 | 20 |
| Day | 21° | 19° | 15° |
| Night | 19° | 17° | 13° |
| Sea | 20° | 19° | 15° |
| Sun | 8 h | 7 h | 6 h |
| Rain days | 8 | 8 | 10 |
More details for September
- Daylight
- 12 h 32 min06:20 – 18:52
- UV index
- 6 · highclear sky, noon (estimate)All months
- Muggy days
- 6 daysdew point 18 °C or moreAll months
- Wind
- 30 km/haverage daily peakAll months
- Cloud cover
- 52 %on averageAll months
- Hot days
- 0 days30 °C or moreAll months
- Snow days
- 0 days1 cm or more of fresh snowAll months
- Time zone
- UTC−4America/New_York
How the score comes together
- Temperatureweight 35 %0 %
- Seaweight 25 %26 %
- Sunshineweight 20 %60 %
- Few rainy daysweight 20 %70 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in September
- Wetsuit for longer swims
- Sunscreen
- Sunglasses & sun hat
- Rain jacket or umbrella
- Windproof jacket
Nantucket in September: quick answers
Is Nantucket hot in September?
No. In September, Nantucket is mild: daytime highs average 19 °C and nights drop to about 17 °C.
Can you swim in Nantucket in September?
Only if you don't mind cold water: in September the sea averages just 18.8 °C. Comfortable swimming is possible in August.
Does it rain much in Nantucket in September?
Rain falls on about 8 days, adding up to 104 mm.
Nantucket month by month
The whole year in NantucketAll destinations: USAWhere to go in SeptemberSea temperature in September
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0). Sources & licences