Frost dates in Grinnell, IA
The average last spring frost in Grinnell is around May 3 and the first fall frost is around October 5. That gives Grinnell an average growing season of about 155 days.
Last spring frost
| Early (10% chance after) | April 16 |
|---|---|
| Average (50%) | May 3 |
| Late (90%) | May 17 |
First fall frost
| Early (10%) | September 21 |
|---|---|
| Average (50%) | October 5 |
| Late (90% chance before) | October 21 |