Grass Valley, Oregon has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 38.9 °F (low) to 60.9 °F (high). Annual precipitation averages 13.4 Inches. Grass Valley is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 26.9 °F | 40.3 °F | 1.82 in. |
| February | 28.5 °F | 44.6 °F | 1.49 in. |
| March | 32.1 °F | 51.7 °F | 1.13 in. |
| April | 35.7 °F | 58.3 °F | 1.08 in. |
| May | 42.2 °F | 67.1 °F | 1.27 in. |
| June | 47.7 °F | 74.2 °F | 0.75 in. |
| July | 54.4 °F | 84.7 °F | 0.28 in. |
| August | 54.5 °F | 84.6 °F | 0.25 in. |
| September | 48.1 °F | 76.6 °F | 0.41 in. |
| October | 39.5 °F | 62.2 °F | 1.06 in. |
| November | 31.6 °F | 47.8 °F | 1.75 in. |
| December | 26.1 °F | 39.2 °F | 2.12 in. |
| Annual | 38.9 °F | 60.9 °F | 13.41 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7a : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 7a : 0°F to 5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |