Last frost date in Ottawa, Illinois
April 27
Average last frost in spring. In an early year (1 in 10) it's over by April 12; in a late year (1 in 10) it comes after May 13.
October 17
Average first frost in fall. 1 year in 10 it comes by October 3.
Source: NOAA U.S. Climate Normals 1991–2020, station Marseilles Lock (USC00115372), 4 miles from Ottawa, elevation 490 ft. NOAA National Centers for Environmental Information. These are long-term averages, not a forecast.
| Early year | Average | Late year | |
|---|---|---|---|
| Last frost in spring | Apr 12 | Apr 27 | May 13 |
| First frost in fall | Oct 3 | Oct 17 | Oct 29 |
Frost-free days in an average year: 171
| Chance in a year | Average last in spring | Average first in fall | |
|---|---|---|---|
| Light frost (36°F) | Every year | May 7 | Oct 7 |
| Frost (32°F) | Every year | Apr 27 | Oct 17 |
| Hard freeze (28°F) | Every year | Apr 15 | Oct 27 |
Nights at 32°F or colder in an average year: 139
What to plant now in Ottawa
- Spring planting calendar for an average last frost around April 30 Ottawa: April 27
- Fall planting calendar for an average first frost around October 20 Ottawa: October 17
Planting dates: USDA Home and Garden Bulletin No. 9 (1967), “Suburban and Farm Vegetable Gardens,” tables 4 and 5. How we match the table.
Nearby in Illinois
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