There is no year-round weather station at Isle Royale. The source of the following climate information is the National Park Foundation and apparently reflects nearby mainland climate information.
The following data was made available through the National Park Foundation.
Isle Royale National Park is open to the public from mid-April through October.
You can go to a version of this information with no tables or graphics.
| TEMPERATURE | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
| Normal Daily Maximum | 11 | 20 | 32 | 45 | 54 | 62 | 68 | 69 | 60 | 52 | 33 | 18 |
| Normal Daily Minimum | -11 | -5 | 9 | 25 | 36 | 43 | 50 | 54 | 47 | 39 | 17 | -1 |
| Extreme High | 48 | 53 | 66 | 70 | 79 | 87 | 89 | 86 | 82 | 72 | 65 | 57 |
| Extreme Low | -46 | -44 | -38 | -5 | 19 | 32 | 37 | 34 | 29 | 12 | -32 | -41 |
| Days Above 90 degrees fahrenheit | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Days Below 32 degrees fahrenheit | 31 | 28 | 30 | 22 | 8 | 0 | 0 | 0 | 1 | 6 | 28 | 31 |
| PRECIPITATION | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
| Normal | 1.2 | 0.9 | 1.8 | 2.2 | 2.5 | 3.1 | 2.5 | 3.2 | 3.4 | 2.1 | 1.7 | 1.3 |
| Maximum | 4.7 | 2.4 | 5.1 | 5.8 | 7.7 | 8.0 | 8.5 | 10.3 | 6.6 | 7.5 | 5.0 | 3.7 |
| Maximum 24 Hour | 1.7 | 1.4 | 2.4 | 2.3 | 2.6 | 2.5 | 2.3 | 1.8 | 4.5 | 1.8 | 2.6 | 2.1 |
| Maximum Snowfall | 47 | 32 | 46 | 32 | 8 | 0 | 0 | 0 | 4 | 9 | 38 | 44 |
| Days With Measureable Precipitation | 12 | 10 | 11 | 11 | 12 | 13 | 11 | 11 | 12 | 10 | 11 | 12 |
| Average Number of Thunderstorms | 0 | 0 | 0 | 0 | 1 | 2 | 2 | 2 | 2 | 1 | 0 | 0 |
Notes: Summers are cool and winters are very cold; periods of warm summer temperatures rarely exceed 2 to 3 days in length. Day to day temperature changes are strongly moderated by the surrounding waters of Lake Superior, the coldest of the Great Lakes.
Go to Virtual Visitor Center for Isle Royale National Park
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