Black Diamond, Washington has a Temperate Oceanic Climate climate (Köppen classification: Cfb). Average annual temperatures range from 42 °F (low) to 59.3 °F (high). Annual precipitation averages 56 Inches. Black Diamond 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 Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 33.9 °F | 45.2 °F | 7.09 in. |
| February | 33.9 °F | 47.9 °F | 5.14 in. |
| March | 35.9 °F | 52.1 °F | 5.98 in. |
| April | 39.1 °F | 57.3 °F | 5.13 in. |
| May | 44.8 °F | 64.6 °F | 3.71 in. |
| June | 48.9 °F | 68.8 °F | 3.25 in. |
| July | 52.7 °F | 75.6 °F | 1.27 in. |
| August | 53.0 °F | 76.6 °F | 1.56 in. |
| September | 48.8 °F | 70.3 °F | 2.63 in. |
| October | 42.5 °F | 59.2 °F | 5.44 in. |
| November | 37.2 °F | 49.8 °F | 7.87 in. |
| December | 33.3 °F | 44.1 °F | 6.95 in. |
| Annual | 42 °F | 59.3 °F | 56.02 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8b : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfb - Temperate Oceanic Climate |