| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7a: 0°F to 5°F |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 6b: -5°F to 0°F |
| 1990 Hardiness Zone: | Zone 6a: -10F to -5F |
| Average First Frost Date: | Oct. 1 - Oct. 10 |
| Average Last Frost Date: | May 11 - May 20 |
| Koppen-Geiger Climate Zone: | BSk - Cold Semi-Arid Climate |
| Ecoregion: | 10a - Channeled Scablands |
| Heat Zone Days: | 31 - 45 days Over 86°F |
Annual Climate Data for ZIP Code 99169 - Ritzville, WA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 23 | 26 | 30 | 35 | 41 | 47 | 53 | 53 | 45 | 36 | 30 | 23 | 37 |
| Avg Max Temp (°F) | 35 | 42 | 52 | 61 | 69 | 77 | 86 | 86 | 76 | 62 | 44 | 35 | 60 |
| Avg Precip (In.) | 1.3 | 1.15 | 1.19 | .9 | 1 | .74 | .54 | .44 | .58 | .89 | 1.64 | 1.74 | 12.1 |