| 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: | 10b - Loess Islands |
| Heat Zone Days: | 31 - 45 days Over 86°F |
Annual Climate Data for ZIP Code 99135 - Hartline, WA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 20 | 24 | 30 | 35 | 42 | 48 | 54 | 54 | 47 | 36 | 28 | 20 | 37 |
| Avg Max Temp (°F) | 33 | 39 | 51 | 61 | 70 | 78 | 86 | 86 | 77 | 61 | 43 | 33 | 60 |
| Avg Precip (In.) | .92 | 1.02 | 1.03 | .82 | 1.1 | .86 | .75 | .49 | .53 | .6 | 1.45 | 1.49 | 11.05 |