Three Rivers, Oregon has a Continental Subarctic - Cold Dry Summer climate (Köppen classification: Dsc). Average annual temperatures range from -1 °C (low) to 15.2 °C (high). Annual precipitation averages 449.3 Millimeters. Three Rivers is located in USDA Plant Hardiness Zone 6a. 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 | -6.2 °C | 4.4 °C | 65.28 mm |
| February | -5.7 °C | 6.3 °C | 45.47 mm |
| March | -4.1 °C | 9.6 °C | 36.07 mm |
| April | -2.4 °C | 13.1 °C | 31.75 mm |
| May | 1 °C | 17.9 °C | 35.31 mm |
| June | 3.5 °C | 22.3 °C | 23.11 mm |
| July | 6.3 °C | 28.5 °C | 13.72 mm |
| August | 5.8 °C | 28.2 °C | 13.97 mm |
| September | 2.2 °C | 24.1 °C | 14.48 mm |
| October | -1.4 °C | 16.4 °C | 36.83 mm |
| November | -4 °C | 8.1 °C | 55.12 mm |
| December | -6.7 °C | 3.4 °C | 78.23 mm |
| Annual | -1 °C | 15.2 °C | 449.34 mm |
| Average First Frost Date | Aug. 21 - Aug. 31 |
| Average Last Frost Date | Jun. 1 - Jun. 10 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Dsc - Continental Subarctic - Cold Dry Summer |