Frost dates in Ontonagon, MI
The average last spring frost in Ontonagon is around May 31 and the first fall frost is around September 25. That gives Ontonagon an average growing season of about 117 days.
Last spring frost
| Early (10% chance after) | May 17 |
|---|---|
| Average (50%) | May 31 |
| Late (90%) | June 17 |
First fall frost
| Early (10%) | September 13 |
|---|---|
| Average (50%) | September 25 |
| Late (90% chance before) | October 8 |