| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 5b: -15°F to -10°F |
| 2012 Hardiness Zone: | Zone 5b: -15°F to -10°F |
| 1990 Hardiness Zone: | Zone 5a: -20F to -15F |
| Average First Frost Date: | Oct. 11 - Oct. 20 |
| Average Last Frost Date: | May 1 - May 10 |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers |
| Ecoregion: | 54a - Illinois/Indiana Prairies |
| Heat Zone Days: | 15 - 30 days Over 86°F |
Annual Climate Data for ZIP Code 61350 - Ottawa, IL | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 12 | 18 | 29 | 39 | 50 | 59 | 63 | 61 | 53 | 41 | 30 | 19 | 39 |
| Avg Max Temp (°F) | 30 | 36 | 48 | 62 | 73 | 82 | 85 | 83 | 77 | 65 | 49 | 35 | 60 |
| Avg Precip (In.) | 1.58 | 1.48 | 2.71 | 3.58 | 4.15 | 4.17 | 3.8 | 3.73 | 3.46 | 2.67 | 3.03 | 2.34 | 36.7 |