Frost dates in O'Fallon, MO
The average last spring frost in O'Fallon is around April 14 and the first fall frost is around October 18. That gives O'Fallon an average growing season of about 187 days.
Last spring frost
| Early (10% chance after) | March 31 |
|---|---|
| Average (50%) | April 14 |
| Late (90%) | May 2 |
First fall frost
| Early (10%) | October 2 |
|---|---|
| Average (50%) | October 18 |
| Late (90% chance before) | November 8 |