Mattawa, Washington has a Cold Desert Climate climate (Köppen classification: BWk). Average annual temperatures range from 41.7 °F (low) to 64.4 °F (high). Annual precipitation averages 7.7 Inches. Mattawa is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 26.3 °F | 39.3 °F | 1.07 in. |
| February | 29.2 °F | 46.6 °F | 0.68 in. |
| March | 34.1 °F | 56.2 °F | 0.71 in. |
| April | 39.8 °F | 64.5 °F | 0.58 in. |
| May | 47.6 °F | 74.0 °F | 0.58 in. |
| June | 54.0 °F | 80.7 °F | 0.64 in. |
| July | 60.3 °F | 90.1 °F | 0.27 in. |
| August | 59.2 °F | 89.0 °F | 0.13 in. |
| September | 50.8 °F | 79.8 °F | 0.18 in. |
| October | 40.5 °F | 64.7 °F | 0.66 in. |
| November | 31.9 °F | 49.0 °F | 0.92 in. |
| December | 26.4 °F | 39.0 °F | 1.25 in. |
| Annual | 41.7 °F | 64.4 °F | 7.67 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : 5°F to 10°F |
| Plant Hardiness Zone - 2012 | Zone 7a : 0°F to 5°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BWk - Cold Desert Climate |