Weather on September 21 at Isle Royale
Isle Royale National Park
Based on 50 years of data from Houghton, MI
Planning Your Visit
September 21st in Isle Royale National Park (via Houghton, MI) typically brings mild fall weather, with average highs around 63°F and lows near 46°F. Over 50 years of records, the warmest September 21st was in 2019 (70°F average), while the coldest was 1974 (38°F) — a 32°F range across recorded history. Rain or other precipitation has occurred on about 58% of September 21st dates historically, with the wettest September 21st recording 5.31" of rain. The last decade has been 6.0°F warmer on this date compared to 20-30 years ago.
The last decade has been 6.0°F warmer on this date compared to 20-30 years ago.
Planning for September 21st in Isle Royale? Great weather for outdoor activities. Consider bringing rain gear or an umbrella.
Year by Year History
| Year | High | Low | Precip | Snow |
|---|---|---|---|---|
| 2025 | 72°F | 59°F | 1.45" | -- |
| 2024 | 76°F | 57°F | 0" | -- |
| 2023 | 82°F | 56°F | 0" | -- |
| 2022 | 69°F | 48°F | 0.18" | -- |
| 2021 | 66°F | 46°F | 0.23" | -- |
| 2020 | 76°F | 57°F | 0" | -- |
| 2019 | 80°F | 61°F | 0.03" | -- |
| 2018 | 66°F | 44°F | 0.43" | -- |
| 2017 | 70°F | 45°F | 0" | -- |
| 2016 | 69°F | 53°F | 0" | -- |
| 2015 | 77°F | 52°F | 0" | -- |
| 2014 | 53°F | 34°F | 0.08" | -- |
| 2013 | 50°F | 38°F | 0.03" | -- |
| 2012 | 53°F | 35°F | 1.7" | -- |
| 2011 | 61°F | 44°F | 0.2" | -- |
| 2010 | 70°F | 50°F | 0.56" | -- |
| 2009 | 70°F | 52°F | 0.3" | -- |
| 2008 | 60°F | 39°F | 0" | -- |
| 2007 | 70°F | 53°F | 5.31" | -- |
| 2006 | 63°F | 42°F | 0" | -- |
| 2005 | 73°F | 47°F | 0" | -- |
| 2004 | 73°F | 56°F | 0" | -- |
| 2003 | 66°F | 47°F | 0.03" | -- |
| 2002 | 62°F | 54°F | 0.79" | 0" |
| 2001 | 68°F | 52°F | 0" | 0" |
| 2000 | 58°F | 41°F | 0.48" | 0" |
| 1999 | 59°F | 36°F | 0" | 0" |
| 1998 | 71°F | 48°F | 0.28" | 0" |
| 1997 | 62°F | 39°F | 0" | 0" |
| 1996 | 66°F | 51°F | 0.05" | 0" |
| 1995 | 51°F | 36°F | 1.24" | 0" |
| 1994 | 75°F | 60°F | 0.48" | 0" |
| 1993 | 64°F | 45°F | 0" | 0" |
| 1992 | 69°F | 49°F | 0" | 0" |
| 1991 | 65°F | 38°F | 0" | 0" |
| 1990 | 57°F | 50°F | 1.3" | 0" |
| 1989 | 65°F | 59°F | 0.99" | 0" |
| 1988 | 56°F | 47°F | 0.05" | 0" |
| 1983 | 49°F | 41°F | 0.1" | 0" |
| 1981 | 50°F | 35°F | 0" | 0" |
| 1980 | 51°F | 43°F | 1.04" | 0" |
| 1979 | 54°F | 43°F | 0" | 0" |
| 1978 | 54°F | 44°F | 0" | 0" |
| 1977 | 61°F | 40°F | 0" | 0" |
| 1976 | 46°F | 37°F | 0.2" | 0" |
| 1975 | 48°F | 39°F | 0.41" | 0" |
| 1974 | 43°F | 33°F | 0.18" | 0" |
| 1973 | 53°F | 34°F | 1.04" | 0" |
| 1972 | 57°F | 40°F | 0" | 0" |
| 1971 | 57°F | 43°F | 0.08" | 0" |