Mossyrock, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 4.9 °C (low) to 16.2 °C (high). Annual precipitation averages 1490.5 Millimeters. Mossyrock is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 0.6 °C | 7.4 °C | 207.77 mm |
| February | 0.6 °C | 9.6 °C | 147.32 mm |
| March | 1.7 °C | 12.2 °C | 160.27 mm |
| April | 3.4 °C | 15.4 °C | 136.4 mm |
| May | 6.4 °C | 19.6 °C | 93.98 mm |
| June | 8.7 °C | 22 °C | 68.07 mm |
| July | 10.6 °C | 26.3 °C | 22.35 mm |
| August | 10.6 °C | 26.4 °C | 29.97 mm |
| September | 8.2 °C | 23 °C | 59.44 mm |
| October | 4.9 °C | 15.8 °C | 138.18 mm |
| November | 2.2 °C | 10.2 °C | 216.66 mm |
| December | 0.3 °C | 6.8 °C | 210.06 mm |
| Annual | 4.9 °C | 16.2 °C | 1490.47 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |