Inchelium, Washington has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 36.1 °F (low) to 60.6 °F (high). Annual precipitation averages 17.2 Inches. Inchelium is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 23.2 °F | 34.6 °F | 2.04 in. |
| February | 23.5 °F | 40.6 °F | 1.5 in. |
| March | 28.9 °F | 51.3 °F | 1.85 in. |
| April | 34.2 °F | 61.3 °F | 1.32 in. |
| May | 41.7 °F | 71.4 °F | 1.41 in. |
| June | 47.5 °F | 77.2 °F | 1.2 in. |
| July | 52.0 °F | 87.4 °F | 0.62 in. |
| August | 50.7 °F | 87.4 °F | 0.41 in. |
| September | 43.8 °F | 77.2 °F | 0.65 in. |
| October | 35.2 °F | 60.1 °F | 1.47 in. |
| November | 29.2 °F | 43.7 °F | 2.06 in. |
| December | 23.1 °F | 34.5 °F | 2.66 in. |
| Annual | 36.1 °F | 60.6 °F | 17.19 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |