Three Rivers, Oregon has a Continental Subarctic - Cold Dry Summer climate (Köppen classification: Dsc). Average annual temperatures range from 30.2 °F (low) to 59.4 °F (high). Annual precipitation averages 17.7 Inches. 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 | 20.9 °F | 40.0 °F | 2.57 in. |
| February | 21.7 °F | 43.4 °F | 1.79 in. |
| March | 24.6 °F | 49.3 °F | 1.42 in. |
| April | 27.6 °F | 55.6 °F | 1.25 in. |
| May | 33.8 °F | 64.2 °F | 1.39 in. |
| June | 38.3 °F | 72.2 °F | 0.91 in. |
| July | 43.4 °F | 83.3 °F | 0.54 in. |
| August | 42.4 °F | 82.8 °F | 0.55 in. |
| September | 36.0 °F | 75.4 °F | 0.57 in. |
| October | 29.5 °F | 61.5 °F | 1.45 in. |
| November | 24.8 °F | 46.6 °F | 2.17 in. |
| December | 19.9 °F | 38.1 °F | 3.08 in. |
| Annual | 30.2 °F | 59.4 °F | 17.69 in. |
| 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 : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dsc - Continental Subarctic - Cold Dry Summer |