Ione, Washington has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 34.8 °F (low) to 57.6 °F (high). Annual precipitation averages 25.9 Inches. Ione is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 21.8 °F | 32.7 °F | 2.8 in. |
| February | 22.7 °F | 39.4 °F | 1.84 in. |
| March | 27.2 °F | 48.2 °F | 2.32 in. |
| April | 32.6 °F | 57.8 °F | 1.95 in. |
| May | 40.5 °F | 67.7 °F | 2.49 in. |
| June | 46.3 °F | 73.4 °F | 2.89 in. |
| July | 50.5 °F | 83.8 °F | 1.25 in. |
| August | 49.6 °F | 84.4 °F | 0.8 in. |
| September | 42.5 °F | 73.7 °F | 1.13 in. |
| October | 34.5 °F | 56.7 °F | 2.15 in. |
| November | 27.9 °F | 40.9 °F | 3.13 in. |
| December | 21.7 °F | 32.5 °F | 3.15 in. |
| Annual | 34.8 °F | 57.6 °F | 25.9 in. |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 1 - May 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 | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |