Chinook, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 7.3 °C (low) to 14.8 °C (high). Annual precipitation averages 2071.4 Millimeters. Chinook is located in USDA Plant Hardiness Zone 9a. 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 | 3.7 °C | 9.5 °C | 315.72 mm |
| February | 3.7 °C | 10.3 °C | 212.34 mm |
| March | 4.6 °C | 11.7 °C | 228.09 mm |
| April | 5.4 °C | 13.6 °C | 169.42 mm |
| May | 8.1 °C | 16.1 °C | 98.04 mm |
| June | 9.9 °C | 17.8 °C | 70.36 mm |
| July | 12.2 °C | 20 °C | 26.16 mm |
| August | 12 °C | 20.8 °C | 37.08 mm |
| September | 10.8 °C | 20.1 °C | 72.39 mm |
| October | 7.8 °C | 16.3 °C | 194.56 mm |
| November | 5.7 °C | 12 °C | 320.29 mm |
| December | 3.4 °C | 9.2 °C | 326.9 mm |
| Annual | 7.3 °C | 14.8 °C | 2071.35 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 20-30 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |