Frost dates in Royal, IA
The average last spring frost in Royal is around May 5 and the first fall frost is around September 30. That gives Royal an average growing season of about 148 days.
Last spring frost
| Early (10% chance after) | April 24 |
|---|---|
| Average (50%) | May 5 |
| Late (90%) | May 20 |
First fall frost
| Early (10%) | September 14 |
|---|---|
| Average (50%) | September 30 |
| Late (90% chance before) | October 11 |