Isle Royale National Park in September
In September, Isle Royale National Park averages a high of 65°F and a low of 44°F, with 3.1 inches of precipitation (rain plus melted snow). About 3,500 people visit, the 4th busiest of 12 (moderate). Days are 12 hours 31 minutes long.
- Quiet
- Moderate
- Busy
- Very busy
- Few or no visits (may be closed)
- Best months
- High / low
- 65° / 44°F
- Precipitation
- 3.1in
- Snow
- 0in
- Daylight
- 12h 31m
- Visitors
- 3,500
- Crowds
- Moderate
September is one of the best months to visit: mild, wet weather with moderate crowds.
Weather 1991–2020 averages at Grand Portage, MN, 41.1 miles from the park's center, 730 ft. Visitors National Park Service recreation visits, average of 2023–2025. Updated .
Other parks in September
| Park | High / low °F | Crowds | Weather |
|---|---|---|---|
| Voyageurs National Park | 66° / 42° | Moderate | Mild, wet |
| Sleeping Bear Dunes National Lakeshore | 69° / 52° | Moderate | Mild, wet |
| Indiana Dunes National Park | 74° / 56° | Moderate | Mild, wet |
| Cuyahoga Valley National Park | 74° / 52° | Busy | Mild, wet |
| Gateway Arch National Park | 81° / 57° | Moderate | Hot |
Closures, reservations and alerts: Isle Royale National Park on nps.gov
All twelve months at Isle Royale · National parks to visit in September