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.
This data has no tables or graphics.
January
Normal Daily Maximum = 11
Normal Daily Minimum = -11
Extreme High = 48
Extreme Low = -46
Days Above 90 degrees fahrenheit = 0
Days Below 32 degrees fahrenheit = 31
February
Normal Daily Maximum = 20
Normal Daily Minimum = -5
Extreme High = 53
Extreme Low = -44
Days Above 90 degrees fahrenheit = 0
Days Below 32 degrees fahrenheit = 28
March
Normal Daily Maximum = 32
Normal Daily Minimum = 9
Extreme High = 66
Extreme Low = -38
Days Above 90 degrees fahrenheit = 0
Days Below 32 degrees fahrenheit = 30
April
Normal Daily Maximum = 45
Normal Daily Minimum = 25
Extreme High = 70
Extreme Low = -5
Days Above 90 degrees fahrenheit = 0
Days Below 32 degrees fahrenheit = 22
May
Normal Daily Maximum = 54
Normal Daily Minimum = 36
Extreme High = 79
Extreme Low = 19
Days Above 90 degrees fahrenheit = 0
Days Below 32 degrees fahrenheit = 8
June
Normal Daily Maximum = 62
Normal Daily Minimum = 43
Extreme High = 87
Extreme Low = 32
Days Above 90 degrees fahrenheit = 0
Days Below 32 degrees fahrenheit = 0
July
Normal Daily Maximum = 68
Normal Daily Minimum = 50
Extreme High = 89
Extreme Low = 37
Days Above 90 degrees fahrenheit = 0
Days Below 32 degrees fahrenheit = 0
August
Normal Daily Maximum = 69
Normal Daily Minimum = 54
Extreme High = 86
Extreme Low = 34
Days Above 90 degrees fahrenheit = 0
Days Below 32 degrees fahrenheit = 0
September
Normal Daily Maximum = 60
Normal Daily Minimum = 47
Extreme High = 82
Extreme Low = 29
Days Above 90 degrees fahrenheit = 0
Days Below 32 degrees fahrenheit = 1
October
Normal Daily Maximum = 52
Normal Daily Minimum = 39
Extreme High = 72
Extreme Low = 12
Days Above 90 degrees fahrenheit = 0
Days Below 32 degrees fahrenheit = 6
November
Normal Daily Maximum = 33
Normal Daily Minimum = 17
Extreme High = 65
Extreme Low = -32
Days Above 90 degrees fahrenheit = 0
Days Below 32 degrees fahrenheit = 28
December
Normal Daily Maximum = 18
Normal Daily Minimum = -1
Extreme High = 57
Extreme Low = -41
Days Above 90 degrees fahrenheit = 0
Days Below 32 degrees fahrenheit = 31
January
Normal = 1.2
Maximum = 4.7
Maximum 24 Hour = 1.7
Maximum Snowfall = 47
Days With Measureable Precipitation = 12
Average Number of Thunderstorms = 0
Percentage Cloudy Days = 62
Percentage Partly Cloudy Days = 18
Percentage Sunny Days = 20
February
Normal = 1.2
Maximum = 4.7
Maximum 24 Hour = 1.7
Maximum Snowfall = 47
Days With Measureable Precipitation = 12
Average Number of Thunderstorms = 0
Percentage Cloudy Days = 57
Percentage Partly Cloudy Days = 20
Percentage Sunny Days = 23
March
Normal = 1.8
Maximum = 5.1
Maximum 24 Hour = 2.4
Maximum Snowfall = 46
Days With Measureable Precipitation = 11
Average Number of Thunderstorms = 0
Percentage Cloudy Days = 57
Percentage Partly Cloudy Days = 21
Percentage Sunny Days = 22
April
Normal = 2.2
Maximum = 5.8
Maximum 24 Hour = 2.3
Maximum Snowfall = 32
Days With Measureable Precipitation = 11
Average Number of Thunderstorms = 0
Percentage Cloudy Days = 56
Percentage Partly Cloudy Days = 24
Percentage Sunny Days = 20
May
Normal = 2.5
Maximum = 7.7
Maximum 24 Hour = 2.6
Maximum Snowfall = 8
Days With Measureable Precipitation = 12
Average Number of Thunderstorms = 1
Percentage Cloudy Days = 55
Percentage Partly Cloudy Days = 25
Percentage Sunny Days = 20
June
Normal = 3.1
Maximum = 8.0
Maximum 24 Hour = 2.5
Maximum Snowfall = 0
Days With Measureable Precipitation = 13
Average Number of Thunderstorms = 2
Percentage Cloudy Days = 54
Percentage Partly Cloudy Days = 29
Percentage Sunny Days = 17
July
Normal = 2.5
Maximum = 8.5
Maximum 24 Hour = 2.3
Maximum Snowfall = 0
Days With Measureable Precipitation = 11
Average Number of Thunderstorms = 2
Percentage Cloudy Days = 37
Percentage Partly Cloudy Days = 43
Percentage Sunny Days = 20
August
Normal = 3.2
Maximum = 10.3
Maximum 24 Hour = 1.8
Maximum Snowfall = 0
Days With Measureable Precipitation = 11
Average Number of Thunderstorms = 2
Percentage Cloudy Days = 38
Percentage Partly Cloudy Days = 41
Percentage Sunny Days = 21
September
Normal = 3.4
Maximum = 6.6
Maximum 24 Hour = 4.5
Maximum Snowfall = 4
Days With Measureable Precipitation = 12
Average Number of Thunderstorms = 2
Percentage Cloudy Days = 55
Percentage Partly Cloudy Days = 25
Percentage Sunny Days = 20
October
Normal = 2.1
Maximum = 7.5
Maximum 24 Hour = 1.8
Maximum Snowfall = 9
Days With Measureable Precipitation = 10
Average Number of Thunderstorms = 1
Percentage Cloudy Days = 57
Percentage Partly Cloudy Days = 23
Percentage Sunny Days = 20
November
Normal = 1.7
Maximum = 5.0
Maximum 24 Hour = 2.6
Maximum Snowfall = 38
Days With Measureable Precipitation = 11
Average Number of Thunderstorms = 0
Percentage Cloudy Days = 64
Percentage Partly Cloudy Days = 19
Percentage Sunny Days = 17
December
Normal = 1.3
Maximum = 3.7
Maximum 24 Hour = 2.1
Maximum Snowfall = 44
Days With Measureable Precipitation = 12
Average Number of Thunderstorms = 0
Percentage Cloudy Days = 58
Percentage Partly Cloudy Days = 21
Percentage Sunny Days = 21
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 Climate Information for Isle Royale National Park
Go to Virtual Visitor Center for Isle Royale National Park
Go to Home Page for Isle Royale National Park
We welcome your comments and suggestions to editor: Smitty Parratt