Frost dates in Roundup, MT
The average last spring frost in Roundup is around May 15 and the first fall frost is around September 22. That gives Roundup an average growing season of about 130 days.
Last spring frost
| Early (10% chance after) | April 28 |
|---|---|
| Average (50%) | May 15 |
| Late (90%) | May 31 |
First fall frost
| Early (10%) | September 4 |
|---|---|
| Average (50%) | September 22 |
| Late (90% chance before) | October 8 |