Frost dates in Great Falls, MT
The average last spring frost in Great Falls is around May 10 and the first fall frost is around September 25. That gives Great Falls an average growing season of about 138 days.
Last spring frost
| Early (10% chance after) | April 20 |
|---|---|
| Average (50%) | May 10 |
| Late (90%) | May 28 |
First fall frost
| Early (10%) | September 13 |
|---|---|
| Average (50%) | September 25 |
| Late (90% chance before) | October 11 |