Fossil, Oregon has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 2.5 °C (low) to 16.8 °C (high). Annual precipitation averages 342.2 Millimeters. 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 | -2.9 °C | 6.2 °C | 35.31 mm |
| February | -2.6 °C | 8.1 °C | 28.19 mm |
| March | -0.7 °C | 11.8 °C | 36.07 mm |
| April | 1.1 °C | 14.7 °C | 33.53 mm |
| May | 4.3 °C | 19.6 °C | 37.59 mm |
| June | 7.1 °C | 23.5 °C | 34.29 mm |
| July | 9.8 °C | 29.9 °C | 10.67 mm |
| August | 9.3 °C | 29.5 °C | 9.14 mm |
| September | 6.1 °C | 24.8 °C | 11.94 mm |
| October | 2.4 °C | 17.5 °C | 32.26 mm |
| November | -0.8 °C | 10.1 °C | 37.85 mm |
| December | -3.3 °C | 5.4 °C | 35.31 mm |
| Annual | 2.5 °C | 16.8 °C | 342.15 mm |
| 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 : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |