Sunnyside, Washington has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 38.7 °F (low) to 64 °F (high). Annual precipitation averages 7.3 Inches. Sunnyside is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 26.1 °F | 39.7 °F | 1.01 in. |
| February | 27.4 °F | 47.1 °F | 0.66 in. |
| March | 31.9 °F | 56.5 °F | 0.51 in. |
| April | 36.6 °F | 64.2 °F | 0.52 in. |
| May | 44.4 °F | 73.3 °F | 0.69 in. |
| June | 50.1 °F | 79.7 °F | 0.68 in. |
| July | 55.0 °F | 88.8 °F | 0.18 in. |
| August | 53.7 °F | 87.5 °F | 0.18 in. |
| September | 46.4 °F | 78.6 °F | 0.25 in. |
| October | 37.6 °F | 64.5 °F | 0.77 in. |
| November | 30.0 °F | 49.5 °F | 0.84 in. |
| December | 25.6 °F | 38.8 °F | 1.01 in. |
| Annual | 38.7 °F | 64 °F | 7.3 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |