| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F |
| 1990 Hardiness Zone: | Zone 1b: -15F to -10F |
| Average First Frost Date: | Oct. 11 - Oct. 20 |
| Average Last Frost Date: | Apr. 11 - Apr. 20 |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers |
| Ecoregion: | 72f - River Hills |
| Heat Zone Days: | 61 - 90 days Over 86°F |
Annual Climate Data for ZIP Code 63090 - Washington, MO | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 20 | 25 | 34 | 44 | 53 | 63 | 67 | 65 | 57 | 45 | 35 | 25 | 44 |
| Avg Max Temp (°F) | 40 | 46 | 57 | 68 | 77 | 86 | 90 | 89 | 81 | 70 | 56 | 44 | 67 |
| Avg Precip (In.) | 2.17 | 2.26 | 3.61 | 3.94 | 4.43 | 3.89 | 3.8 | 3.39 | 3.45 | 3.12 | 3.99 | 2.91 | 40.94 |