Seneca, Oregon has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from -3.1 °C (low) to 14 °C (high). Annual precipitation averages 352 Millimeters. Seneca is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Jun. 21 - Jun. 30 through the first frost around July 11 - July 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.8 °C | 2.2 °C | 39.12 mm |
| February | -8.8 °C | 4.7 °C | 26.67 mm |
| March | -5.7 °C | 8.1 °C | 33.27 mm |
| April | -3.2 °C | 11.5 °C | 29.21 mm |
| May | 0.3 °C | 16.6 °C | 45.72 mm |
| June | 2.8 °C | 21.3 °C | 29.97 mm |
| July | 5 °C | 28.2 °C | 11.68 mm |
| August | 3.5 °C | 28.1 °C | 10.67 mm |
| September | -0.2 °C | 23.2 °C | 16.51 mm |
| October | -4.3 °C | 15 °C | 28.7 mm |
| November | -6.8 °C | 6.8 °C | 36.58 mm |
| December | -10.3 °C | 2 °C | 43.94 mm |
| Annual | -3.1 °C | 14 °C | 352.04 mm |
| Average First Frost Date | July 11 - July 20 |
| Average Last Frost Date | Jun. 21 - Jun. 30 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |