Frost dates in Johnston, IA
The average last spring frost in Johnston is around April 22 and the first fall frost is around October 17. That gives Johnston an average growing season of about 178 days.
Last spring frost
| Early (10% chance after) | April 9 |
|---|---|
| Average (50%) | April 22 |
| Late (90%) | May 4 |
First fall frost
| Early (10%) | October 2 |
|---|---|
| Average (50%) | October 17 |
| Late (90% chance before) | October 28 |