| 2023 Hardiness Zone: | 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: | Rare Over 86°F |
Annual Climate Data for ZIP Code 60543 - Oswego, IL | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 12 | 17 | 27 | 37 | 47 | 57 | 62 | 60 | 51 | 40 | 29 | 18 | 38 |
| Avg Max Temp (°F) | 30 | 35 | 47 | 60 | 72 | 81 | 84 | 82 | 76 | 64 | 48 | 35 | 59 |
| Avg Precip (In.) | 1.66 | 1.53 | 2.57 | 3.75 | 3.97 | 4.35 | 4.14 | 4.14 | 3.41 | 2.69 | 3.1 | 2.38 | 37.69 |