SeaTac, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 44.3 °F (low) to 60.5 °F (high). Annual precipitation averages 43.8 Inches. SeaTac is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 1 - Mar. 10 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 36.0 °F | 46.9 °F | 6.18 in. |
| February | 35.9 °F | 49.4 °F | 4.37 in. |
| March | 38.3 °F | 53.3 °F | 4.9 in. |
| April | 41.6 °F | 58.7 °F | 3.69 in. |
| May | 46.9 °F | 65.6 °F | 2.14 in. |
| June | 51.3 °F | 69.9 °F | 1.65 in. |
| July | 54.9 °F | 76.5 °F | 0.76 in. |
| August | 55.1 °F | 77.0 °F | 0.89 in. |
| September | 51.4 °F | 71.1 °F | 1.56 in. |
| October | 45.1 °F | 60.2 °F | 4.62 in. |
| November | 39.2 °F | 51.2 °F | 6.62 in. |
| December | 35.6 °F | 46.0 °F | 6.44 in. |
| Annual | 44.3 °F | 60.5 °F | 43.82 in. |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 1 - Mar. 10 |
| Average Days With Frost | 20-30 Days |
| Plant Hardiness Zone | Zone 9a : 20°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |