Roslyn, Washington has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 35.6 °F (low) to 55.2 °F (high). Annual precipitation averages 42.4 Inches. Roslyn is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 24.0 °F | 34.7 °F | 6.88 in. |
| February | 24.1 °F | 39.5 °F | 4.9 in. |
| March | 27.6 °F | 46.1 °F | 3.64 in. |
| April | 32.5 °F | 53.2 °F | 2.26 in. |
| May | 39.6 °F | 62.1 °F | 1.79 in. |
| June | 46.0 °F | 67.9 °F | 1.17 in. |
| July | 51.6 °F | 77.4 °F | 0.62 in. |
| August | 50.9 °F | 78.5 °F | 0.49 in. |
| September | 43.4 °F | 70.6 °F | 1.36 in. |
| October | 35.1 °F | 56.3 °F | 4.41 in. |
| November | 28.4 °F | 42.0 °F | 6.67 in. |
| December | 23.5 °F | 34.1 °F | 8.16 in. |
| Annual | 35.6 °F | 55.2 °F | 42.35 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 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 | Dsb - Humid Continental Climate - Dry Cool Summer |