SeasonMapNantucket weather in September
United States
September in Nantucket: nice, rainy, with clean air — a great time to visit.
#4 of 12 months in Nantucket · #814 of 1383 destinations to visit in September · comfort 76/100 (tier B)
Updated September 2026 · climate normals from ERA5 reanalysis
Traveller notes on Nantucket in September
Other months in Nantucket
Nantucket's forum rates July for warm, sunny days, with one recurring caveat worth knowing before booking a beach-heavy trip: the ocean itself stays genuinely chilly until August catches up, so swimming is more bracing than the air temperature would suggest. Regulars who want both warm water and warm air tend to point toward September instead.
Add your own note from Nantucket's card on the map.
Nantucket climate normals — September
| Daytime high | 22°C / 72°F | 😎 nice |
|---|---|---|
| Nighttime low | 15°C / 59°F | |
| Feels like (high) | 22°C / 72°F | |
| Sea temperature | 20°C / 68°F | 🌊 fresh |
| Rainfall | 106 mm / 4.2 in | 🌧 rainy |
| Rainy days | 6 days | |
| Humidity | 84% | 💦 very humid |
| Dew point | 16°C / 60°F | |
| Sunshine | 8.9 h/day | |
| Daylight | 12.5 h | |
| Wind | 31 km/h / 19 mph | |
| Air quality (US AQI) | 48 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Crowds in Nantucket in September
How busy the place itself is — school and mass holidays, the months an editor tagged, and how sought-after the weather makes them. Never part of the comfort score.
BusySummer break in United States(estimated)
Peak crowdsBusyShoulder seasonQuiet
Best months for Nantucket's weather
Ranked by this destination's own climate comfort score across the year — a different thing from how busy it gets (see Crowds above).
Fair weatherNantucket's weather peaks June–August.
Best weatherFair weatherToughest weather
What's on in Nantucket in September
Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.
- Hazard
Tick season
1 Apr – 31 Oct · usuallyInsect seasonThe island's deer ticks carry Lyme, babesiosis and tularemia at rates among the highest anywhere, and the moors and bike-path verges are where they wait. Long trousers, and a check at the end of every day. Source ↗
- Season
Sea warm enough to swim
15 Jul – 20 Sep · usuallyThe island sits far enough offshore that the water lags the air by a month. The harbour beaches on the sound side are always several degrees warmer than the south shore. Source ↗
- Season
The quiet weeks
8 Sep – 20 Oct · usuallySeptember and early October keep the warm water and lose the crowd, and the moors out towards Altar Rock turn red. Ferries thin out again after Columbus Day weekend.
Nearby, and something's on
Within 300 km of Nantucket — a day trip or a short hop — with something on this month. Never part of the comfort score.
Where is Nantucket?
Nantucket in September — FAQ
- Is September a good time to visit Nantucket?
- September in Nantucket: nice, rainy, with clean air — a great time to visit. It ranks #4 of 12 months for Nantucket on SeasonMap's comfort score (76/100).
- What is the weather like in Nantucket in September?
- In September, Nantucket averages a daily high of 22.2°C and a low of 15.2°C, with about 105.9 mm of rain over roughly 6.3 rainy days.
- What is the air quality in Nantucket in September?
- Nantucket has a mean US Air Quality Index of about 48 in September.
Other months in Nantucket
Compare Nantucket in September
Warmer or cooler than Nantucket in September
Similar destinations in North America — September
Within 300 km: Boston's Whales on Stellwagen Bank around 15 Apr – 20 Oct, and Newport's Summer season on 20 Jun – 7 Sep.