Hermiston, Oregon has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 41.5 °F (low) to 65.3 °F (high). Annual precipitation averages 8.9 Inches. Hermiston is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 28.5 °F | 41.9 °F | 1.21 in. |
| February | 29.3 °F | 47.9 °F | 0.9 in. |
| March | 33.8 °F | 57.3 °F | 0.82 in. |
| April | 39.4 °F | 64.9 °F | 0.75 in. |
| May | 46.8 °F | 73.9 °F | 0.89 in. |
| June | 52.9 °F | 80.6 °F | 0.58 in. |
| July | 58.7 °F | 90.2 °F | 0.14 in. |
| August | 57.7 °F | 89.3 °F | 0.21 in. |
| September | 49.6 °F | 80.0 °F | 0.31 in. |
| October | 40.1 °F | 65.4 °F | 0.81 in. |
| November | 32.8 °F | 50.6 °F | 1.04 in. |
| December | 28.5 °F | 41.3 °F | 1.21 in. |
| Annual | 41.5 °F | 65.3 °F | 8.87 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : 5°F to 10°F |
| Plant Hardiness Zone - 2012 | Zone 7a : 0°F to 5°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |