Ione, Washington has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.6 °C (low) to 14.2 °C (high). Annual precipitation averages 657.9 Millimeters. 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 | -5.7 °C | 0.4 °C | 71.12 mm |
| February | -5.2 °C | 4.1 °C | 46.74 mm |
| March | -2.7 °C | 9 °C | 58.93 mm |
| April | 0.3 °C | 14.3 °C | 49.53 mm |
| May | 4.7 °C | 19.8 °C | 63.25 mm |
| June | 7.9 °C | 23 °C | 73.41 mm |
| July | 10.3 °C | 28.8 °C | 31.75 mm |
| August | 9.8 °C | 29.1 °C | 20.32 mm |
| September | 5.8 °C | 23.2 °C | 28.7 mm |
| October | 1.4 °C | 13.7 °C | 54.61 mm |
| November | -2.3 °C | 4.9 °C | 79.5 mm |
| December | -5.7 °C | 0.3 °C | 80.01 mm |
| Annual | 1.6 °C | 14.2 °C | 657.87 mm |
| 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 : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |