Tri-City, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.7 °C (low) to 19.7 °C (high). Annual precipitation averages 878.8 Millimeters. Tri-City is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.3 °C | 9.7 °C | 135.64 mm |
| February | 1.6 °C | 12.2 °C | 96.01 mm |
| March | 2.6 °C | 14.8 °C | 94.23 mm |
| April | 4.2 °C | 18.1 °C | 78.49 mm |
| May | 6.9 °C | 22.6 °C | 55.88 mm |
| June | 9.4 °C | 26.3 °C | 25.15 mm |
| July | 11.9 °C | 31.2 °C | 6.86 mm |
| August | 11.3 °C | 31.4 °C | 8.13 mm |
| September | 8.6 °C | 28.1 °C | 20.32 mm |
| October | 5.3 °C | 20.8 °C | 57.4 mm |
| November | 3.4 °C | 12.8 °C | 124.71 mm |
| December | 1.3 °C | 8.7 °C | 176.02 mm |
| Annual | 5.7 °C | 19.7 °C | 878.84 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 30-40 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |