SeasonMapMackinac Island weather in September
United States
September in Mackinac Island: nice, a little rain, with clean air — an excellent time to visit.
#3 of 12 months in Mackinac Island · #605 of 1383 destinations to visit in September · comfort 82/100 (tier A)
Updated September 2026 · climate normals from ERA5 reanalysis
Traveller notes on Mackinac Island in September
Other months in Mackinac Island
Mackinac Island's forum describes August as pleasant but genuinely variable day to day — layers are the standard advice, since a warm afternoon can follow a cool morning within the same visit. Regulars single out the last week of August specifically: cooler nights, thinner crowds, and still enough warm water for a short dip before Labor Day arrives.
Add your own note from Mackinac Island's card on the map.
Mackinac Island climate normals — September
| Daytime high | 20°C / 68°F | 😎 nice |
|---|---|---|
| Nighttime low | 12°C / 54°F | |
| Feels like (high) | 20°C / 68°F | |
| Rainfall | 71 mm / 2.8 in | 🌦 some rain |
| Rainy days | 10 days | |
| Humidity | 78% | 💦 very humid |
| Dew point | 13°C / 55°F | |
| Sunshine | 9.5 h/day | |
| Daylight | 12.5 h | |
| Wind | 21 km/h / 13 mph | |
| Air quality (US AQI) | 41 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Crowds in Mackinac Island 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 crowdsMackinac Bridge Walk, Summer break in United States(estimated)
Peak crowdsBusyShoulder seasonQuiet
Best months for Mackinac Island'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).
Best weatherMackinac Island's weather peaks July–September, best around August.
September includes Mackinac Bridge Walk.
Best weatherFair weatherToughest weather
What's on in Mackinac Island in September
Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.
- Rule
No motor vehicles
1 Jan – 31 DecClosuresCars have been banned since 1898, so everything moves by horse, bicycle or foot, including the luggage and the rubbish. Bring shoes you can walk eight miles round the island in. Source ↗
- Season
Grand Hotel's season
1 May – 31 Oct · usuallyOff-season shutdownClosuresThe big porch hotel opens at the start of May and closes at the end of October, and the rest of the island's rooms run a similar window. Outside it there is almost nowhere to stay at all. Source ↗
- Festival
Mackinac Bridge Walk
30 Aug – 8 Sep · usuallyMajor festivalCrowdedClosuresTens of thousands walk the five miles across the straits on Labor Day morning, which closes the bridge and fills every room in St Ignace and Mackinaw City. It has run since 1958. Source ↗
- Nature
Fall colour
25 Sep – 20 Oct · usuallyAutumn colourThe hardwood on the island's interior turns in the first half of October, the day-trip crowds are gone and the carriage roads are yours. Book before the hotels shut for the winter.
Where is Mackinac Island?
Mackinac Island in September — FAQ
- Is September a good time to visit Mackinac Island?
- September in Mackinac Island: nice, a little rain, with clean air — an excellent time to visit. It ranks #3 of 12 months for Mackinac Island on SeasonMap's comfort score (82/100).
- What is the weather like in Mackinac Island in September?
- In September, Mackinac Island averages a daily high of 20.1°C and a low of 12.4°C, with about 71.1 mm of rain over roughly 9.5 rainy days.
- What is the air quality in Mackinac Island in September?
- Mackinac Island has a mean US Air Quality Index of about 41 in September.