SeaTac, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.8 °C (low) to 15.8 °C (high). Annual precipitation averages 1113 Millimeters. 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 | 2.2 °C | 8.3 °C | 156.97 mm |
| February | 2.2 °C | 9.7 °C | 111 mm |
| March | 3.5 °C | 11.8 °C | 124.46 mm |
| April | 5.3 °C | 14.8 °C | 93.73 mm |
| May | 8.3 °C | 18.7 °C | 54.36 mm |
| June | 10.7 °C | 21.1 °C | 41.91 mm |
| July | 12.7 °C | 24.7 °C | 19.3 mm |
| August | 12.8 °C | 25 °C | 22.61 mm |
| September | 10.8 °C | 21.7 °C | 39.62 mm |
| October | 7.3 °C | 15.7 °C | 117.35 mm |
| November | 4 °C | 10.7 °C | 168.15 mm |
| December | 2 °C | 7.8 °C | 163.58 mm |
| Annual | 6.8 °C | 15.8 °C | 1113.04 mm |
| 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 : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |