Coulee City, Washington has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 3.5 °C (low) to 16.1 °C (high). Annual precipitation averages 242.6 Millimeters. Coulee City 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.8 °C | 1.6 °C | 32.51 mm |
| February | -3.3 °C | 5.3 °C | 21.59 mm |
| March | -0.5 °C | 11.1 °C | 23.37 mm |
| April | 2.2 °C | 16.2 °C | 19.56 mm |
| May | 6.5 °C | 21.5 °C | 21.59 mm |
| June | 9.8 °C | 25.5 °C | 19.3 mm |
| July | 13.4 °C | 31 °C | 9.65 mm |
| August | 13.1 °C | 30.8 °C | 5.59 mm |
| September | 8.7 °C | 25.2 °C | 6.86 mm |
| October | 3.2 °C | 16.5 °C | 18.54 mm |
| November | -1.4 °C | 7.4 °C | 27.94 mm |
| December | -4.7 °C | 1.6 °C | 36.07 mm |
| Annual | 3.5 °C | 16.1 °C | 242.57 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 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 | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |