Fossil, Oregon has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 36.5 °F (low) to 62.2 °F (high). Annual precipitation averages 13.5 Inches. Fossil is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Jun. 1 - Jun. 10 through the first frost around Aug. 21 - Aug. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 26.7 °F | 43.2 °F | 1.39 in. |
| February | 27.4 °F | 46.6 °F | 1.11 in. |
| March | 30.7 °F | 53.2 °F | 1.42 in. |
| April | 33.9 °F | 58.5 °F | 1.32 in. |
| May | 39.7 °F | 67.3 °F | 1.48 in. |
| June | 44.8 °F | 74.3 °F | 1.35 in. |
| July | 49.6 °F | 85.9 °F | 0.42 in. |
| August | 48.8 °F | 85.1 °F | 0.36 in. |
| September | 42.9 °F | 76.6 °F | 0.47 in. |
| October | 36.3 °F | 63.5 °F | 1.27 in. |
| November | 30.5 °F | 50.1 °F | 1.49 in. |
| December | 26.1 °F | 41.7 °F | 1.39 in. |
| Annual | 36.5 °F | 62.2 °F | 13.47 in. |
| Average First Frost Date | Aug. 21 - Aug. 31 |
| Average Last Frost Date | Jun. 1 - Jun. 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 7a : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |