Rosalia, Washington has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 36.4 °F (low) to 59.1 °F (high). Annual precipitation averages 18.3 Inches. Rosalia is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 24.9 °F | 36.8 °F | 2.22 in. |
| February | 26.1 °F | 41.3 °F | 1.6 in. |
| March | 30.1 °F | 49.3 °F | 1.87 in. |
| April | 34.6 °F | 57.3 °F | 1.6 in. |
| May | 41.1 °F | 66.5 °F | 1.66 in. |
| June | 46.6 °F | 72.7 °F | 1.37 in. |
| July | 50.6 °F | 84.3 °F | 0.54 in. |
| August | 50.2 °F | 84.8 °F | 0.45 in. |
| September | 43.2 °F | 75.2 °F | 0.61 in. |
| October | 35.2 °F | 60.0 °F | 1.57 in. |
| November | 29.5 °F | 44.7 °F | 2.34 in. |
| December | 24.3 °F | 35.7 °F | 2.42 in. |
| Annual | 36.4 °F | 59.1 °F | 18.25 in. |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |