Steilacoom, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 43.1 °F (low) to 60.8 °F (high). Annual precipitation averages 42.3 Inches. Steilacoom 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 | 35.0 °F | 47.1 °F | 6.17 in. |
| February | 34.7 °F | 49.8 °F | 4.13 in. |
| March | 37.0 °F | 54.0 °F | 4.7 in. |
| April | 40.2 °F | 58.8 °F | 3.33 in. |
| May | 45.7 °F | 65.8 °F | 2.25 in. |
| June | 50.4 °F | 70.2 °F | 1.59 in. |
| July | 53.9 °F | 76.6 °F | 0.54 in. |
| August | 54.0 °F | 77.3 °F | 1.05 in. |
| September | 49.7 °F | 71.6 °F | 1.52 in. |
| October | 43.5 °F | 60.2 °F | 4.12 in. |
| November | 38.0 °F | 51.6 °F | 6.55 in. |
| December | 34.5 °F | 46.1 °F | 6.38 in. |
| Annual | 43.1 °F | 60.8 °F | 42.33 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 | Csb - Warm-Summer Mediterranean Climate |