SeasonMapHyannis (Cape Cod) weather in September
United States
September in Hyannis: nice, rainy, with clean air — a great time to visit.
#4 of 12 months in Hyannis · #747 of 1383 destinations to visit in September · comfort 78/100 (tier B)
Updated September 2026 · climate normals from ERA5 reanalysis
Traveller notes on Hyannis in September
No notes yet. Open Hyannis on the map to add the first one.
Hyannis climate normals — September
| Daytime high | 23°C / 73°F | 😎 nice |
|---|---|---|
| Nighttime low | 14°C / 58°F | |
| Feels like (high) | 23°C / 73°F | |
| Sea temperature | 23°C / 73°F | 🙂 pleasant |
| Rainfall | 113 mm / 4.5 in | 🌧 rainy |
| Rainy days | 8 days | |
| Humidity | 80% | 💦 very humid |
| Dew point | 15°C / 59°F | |
| Sunshine | 8.6 h/day | |
| Daylight | 12.5 h | |
| Wind | 23 km/h / 14 mph | |
| Air quality (US AQI) | 43 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Crowds in Hyannis 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.
Peak crowdsIsland ferry high season, Summer break in United States(estimated)
Peak crowdsBusyShoulder seasonQuiet
Best months for Hyannis'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 weatherHyannis's weather peaks June–August, best around July.
Best weatherFair weatherToughest weather
What's on in Hyannis in September
Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.
- Opening
Island ferry high season
20 May – 15 Oct · usuallySummer season opensCrowdedBook earlyHyannis is the mainland end of the Nantucket boats, and the summer timetable adds fast ferries and extra sailings from late May. Car spaces on the traditional boat are released months ahead and go the day they open. Source ↗
- Nature
White shark season
1 Jun – 31 Oct · usuallyWildlife seasonRiskWhite sharks follow the grey seals into Cape waters from early summer and are gone by late autumn, with the tagged detections peaking in August and September. It is the ocean side that closes for sightings, not the calmer Nantucket Sound beaches in town. Source ↗
- Hazard
Hurricane season
15 Aug – 31 Oct · usuallyClosuresNew England catches the tail of Atlantic systems in late summer and autumn, and even a passing storm cancels the island ferries and takes the power out for a day or two. Direct hits are rare; disrupted travel is not. Source ↗
Nearby, and something's on
Within 300 km of Hyannis — a day trip or a short hop — with something on this month. Never part of the comfort score.
Where is Hyannis?
Hyannis in September — FAQ
- Is September a good time to visit Hyannis?
- September in Hyannis: nice, rainy, with clean air — a great time to visit. It ranks #4 of 12 months for Hyannis on SeasonMap's comfort score (78/100).
- What is the weather like in Hyannis in September?
- In September, Hyannis averages a daily high of 22.8°C and a low of 14.3°C, with about 113.4 mm of rain over roughly 7.8 rainy days.
- What is the air quality in Hyannis in September?
- Hyannis has a mean US Air Quality Index of about 43 in September.
Other months in Hyannis
Compare Hyannis in September
Warmer or cooler than Hyannis in September
Similar destinations in North America — September
Within 300 km: Boston's Whales on Stellwagen Bank around 15 Apr – 20 Oct, and Nantucket's Sea warm enough to swim around 15 Jul – 20 Sep.