Sunnyside, Washington has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 3.7 °C (low) to 17.8 °C (high). Annual precipitation averages 185.4 Millimeters. 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 | -3.3 °C | 4.3 °C | 25.65 mm |
| February | -2.6 °C | 8.4 °C | 16.76 mm |
| March | -0.1 °C | 13.6 °C | 12.95 mm |
| April | 2.6 °C | 17.9 °C | 13.21 mm |
| May | 6.9 °C | 22.9 °C | 17.53 mm |
| June | 10.1 °C | 26.5 °C | 17.27 mm |
| July | 12.8 °C | 31.6 °C | 4.57 mm |
| August | 12.1 °C | 30.8 °C | 4.57 mm |
| September | 8 °C | 25.9 °C | 6.35 mm |
| October | 3.1 °C | 18.1 °C | 19.56 mm |
| November | -1.1 °C | 9.7 °C | 21.34 mm |
| December | -3.6 °C | 3.8 °C | 25.65 mm |
| Annual | 3.7 °C | 17.8 °C | 185.41 mm |
| 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 : -15°C to -12.2°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |