Royal City, Washington has a Cold Desert Climate climate (Köppen classification: BWk). Average annual temperatures range from 40.2 °F (low) to 62.7 °F (high). Annual precipitation averages 7.7 Inches. Royal City is located in USDA Plant Hardiness Zone 7a. 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 | 25.3 °F | 37.8 °F | 1.02 in. |
| February | 28.1 °F | 44.9 °F | 0.66 in. |
| March | 32.9 °F | 54.6 °F | 0.69 in. |
| April | 38.5 °F | 62.9 °F | 0.63 in. |
| May | 46.0 °F | 72.1 °F | 0.55 in. |
| June | 51.9 °F | 78.7 °F | 0.66 in. |
| July | 58.1 °F | 87.8 °F | 0.38 in. |
| August | 57.3 °F | 87.0 °F | 0.17 in. |
| September | 49.5 °F | 78.2 °F | 0.22 in. |
| October | 39.5 °F | 63.6 °F | 0.65 in. |
| November | 30.7 °F | 47.6 °F | 0.9 in. |
| December | 24.9 °F | 37.1 °F | 1.12 in. |
| Annual | 40.2 °F | 62.7 °F | 7.65 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BWk - Cold Desert Climate |