Isle Royale weather, month by month
- Jul high
- 77°F
- hottest month
- Feb low
- 9°F
- coldest month
- Rain + snowmelt
- 31.6in / yr
- wettest: Sep
- Snowfall
- —in / yr
- rare
- Days ≥ 90°F
- 2/ yr
- Nights ≤ 32°F
- 194/ yr
Jacobsville
Month by month
| Month | High | Low | Rain | Wet days | Sunrise | Sunset | Daylight | Crowds |
|---|---|---|---|---|---|---|---|---|
| Jan | 24° | 9° | 2.0″ | 19 | 8:40 AM | 5:29 PM | 8h 49m | 0 |
| Feb | 25° | 9° | 1.4″ | 14 | 8:02 AM | 6:17 PM | 10h 15m | 0 |
| Mar | 34° | 13° | 1.5″ | 10 | 8:09 AM | 8:00 PM | 11h 51m | 0 |
| Apr | 46° | 27° | 2.9″ | 12 | 7:06 AM | 8:45 PM | 13h 39m | 1 |
| May | 60° | 36° | 3.4″ | 13 | 6:17 AM | 9:27 PM | 15h 10m | 17 |
| Jun | 70° | 45° | 3.3″ | 13 | 5:55 AM | 9:56 PM | 16h 01m | 68 |
| Jul | 77° | 51° | 3.2″ | 11 | 6:11 AM | 9:51 PM | 15h 40m | 100 |
| Aug | 75° | 50° | 2.8″ | 12 | 6:50 AM | 9:10 PM | 14h 20m | 100 |
| Sep | 67° | 44° | 3.5″ | 14 | 7:32 AM | 8:09 PM | 12h 37m | 39 |
| Oct | 53° | 35° | 3.0″ | 16 | 8:14 AM | 7:08 PM | 10h 53m | 2 |
| Nov | 40° | 25° | 2.4″ | 15 | 8:01 AM | 5:18 PM | 9h 17m | 0 |
| Dec | 29° | 16° | 2.4″ | 18 | 8:38 AM | 5:02 PM | 8h 24m | 0 |
Sweet spot: May and September combine average highs between 55°F and 85°F with crowds under 60% of the peak month. Check what is open in those months — quiet can also mean closed roads.
How to read this
These are NOAA’s official 1991–2020 climate normals for one weather station, not a model of the whole park. The station is the one with complete temperature and precipitation normals nearest to a visitor center. Highs and lows are daily averages for the month; “wet days” are days with at least 0.01 inch of precipitation. Mountain parks can be 10–20 °F cooler at their high points than at the station, and the NPS weather page for Isle Royale is the place for current conditions and seasonal closures.
Sunrise and sunset are computed with the NOAA solar equations for the park’s coordinates and shown in America/New York time for the 15th of each month of 2027; they are accurate to about a minute.
Sources · 3
- 1.U.S. Climate Normals 1991–2020 — monthly normals station inventory · National Centers for Environmental Information (NOAA)
- 2.Isle Royale National Park — Weather (nps.gov) · National Park Service
- 3.Isle Royale National Park — Visitor Use Statistics · National Park Service (IRMA)
FAQ
Isle Royale weather questions
- What is the hottest month at Isle Royale?
- July, with an average high of 77°F and an average low of 51°F at Jacobsville (NOAA 1991–2020 normals). The station averages 2 days a year at or above 90°F.
- How cold does Isle Royale get in winter?
- February is the coldest month, averaging a low of 9°F and a high of 25°F at Jacobsville. About 194 nights a year drop to freezing or below.
- Does it snow at Isle Royale?
- Jacobsville records almost no snowfall (no snow normals). Higher elevations in the park can differ.
- When is the rainy season at Isle Royale?
- September is the wettest month on average (3.5 inches of precipitation at Jacobsville); the station's annual total is 31.6 inches.
- How many hours of daylight does Isle Royale get?
- About 16h 01m on June 15 and 8h 24m on December 15 (sunrise 5:55 AM, sunset 9:56 PM in June; 8:38 AM to 5:02 PM in December, America/New York time).
- What is the best month to visit Isle Royale for weather?
- By NOAA's normals, average highs sit between 55°F and 85°F in May, June, July, August and September. Of those, May and September are also well below the park's peak crowds. Weather in the park varies with elevation; this is the Jacobsville station.
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