Umatilla, Oregon has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 5.5 °C (low) to 18.7 °C (high). Annual precipitation averages 230.9 Millimeters. Umatilla 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -1.8 °C | 5.6 °C | 30.23 mm |
| February | -1.5 °C | 8.9 °C | 22.35 mm |
| March | 1.1 °C | 14.2 °C | 21.59 mm |
| April | 4.4 °C | 18.6 °C | 18.03 mm |
| May | 8.6 °C | 23.6 °C | 22.61 mm |
| June | 12 °C | 27.3 °C | 16 mm |
| July | 15.2 °C | 32.6 °C | 4.32 mm |
| August | 14.7 °C | 32.1 °C | 5.59 mm |
| September | 10 °C | 26.9 °C | 9.65 mm |
| October | 4.7 °C | 18.8 °C | 20.83 mm |
| November | 0.7 °C | 10.5 °C | 26.16 mm |
| December | -1.7 °C | 5.3 °C | 33.53 mm |
| Annual | 5.5 °C | 18.7 °C | 230.89 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : -15°C to -12.2°C |
| Plant Hardiness Zone - 2012 | Zone 7b : -15°C to -12.2°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |