Marrowstone, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.4 °C (low) to 14.4 °C (high). Annual precipitation averages 631 Millimeters. Marrowstone is located in USDA Plant Hardiness Zone 9a. 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 | 2.7 °C | 7.9 °C | 75.69 mm |
| February | 2.4 °C | 9 °C | 55.88 mm |
| March | 3.5 °C | 11.1 °C | 69.6 mm |
| April | 5.2 °C | 13.6 °C | 51.82 mm |
| May | 7.6 °C | 16.6 °C | 42.67 mm |
| June | 9.7 °C | 18.6 °C | 38.1 mm |
| July | 11 °C | 21.7 °C | 20.57 mm |
| August | 11.1 °C | 22.3 °C | 17.78 mm |
| September | 9.4 °C | 19.2 °C | 30.23 mm |
| October | 6.7 °C | 14.3 °C | 54.36 mm |
| November | 4.3 °C | 10.4 °C | 89.92 mm |
| December | 2.6 °C | 7.7 °C | 84.33 mm |
| Annual | 6.4 °C | 14.4 °C | 630.95 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |