| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7b: 5°F to 10°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 Zone 7a: 0°F to 5°F |
| 1990 Hardiness Zone: | Zone 6b: -5F to 0F |
| Average First Frost Date: | Oct. 11 - Oct. 20 |
| Average Last Frost Date: | May 11 - May 20 |
| Koppen-Geiger Climate Zone: | Dsb - Humid Continental Climate - Dry Cool Summer |
| Ecoregion: | 10a - Channeled Scablands |
| Heat Zone Days: | 31 - 45 days Over 86°F |
Annual Climate Data for ZIP Code 99133 - Grand Coulee, WA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 20 | 25 | 30 | 36 | 44 | 50 | 56 | 55 | 47 | 37 | 30 | 22 | 38 |
| Avg Max Temp (°F) | 32 | 40 | 51 | 61 | 70 | 78 | 86 | 86 | 76 | 61 | 43 | 33 | 60 |
| Avg Precip (In.) | 1.02 | 1.01 | .97 | .82 | 1.28 | .93 | .66 | .48 | .55 | .6 | 1.31 | 1.49 | 11.12 |