Tonasket, Washington has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 3.7 °C (low) to 16.5 °C (high). Annual precipitation averages 322.3 Millimeters. Tonasket is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.6 °C | 1.2 °C | 29.97 mm |
| February | -3.5 °C | 5.3 °C | 22.61 mm |
| March | -0.4 °C | 11.8 °C | 25.15 mm |
| April | 2.8 °C | 17.6 °C | 24.13 mm |
| May | 6.9 °C | 22.9 °C | 37.85 mm |
| June | 10.5 °C | 26.4 °C | 36.83 mm |
| July | 13.6 °C | 31.5 °C | 16 mm |
| August | 13 °C | 31.1 °C | 13.72 mm |
| September | 8.2 °C | 25.3 °C | 13.46 mm |
| October | 3.1 °C | 16.4 °C | 26.16 mm |
| November | -1.2 °C | 7.3 °C | 34.04 mm |
| December | -4.2 °C | 1.6 °C | 42.42 mm |
| Annual | 3.7 °C | 16.5 °C | 322.34 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |