Sekiu, Washington has a Temperate Oceanic Climate climate (Köppen classification: Cfb). Average annual temperatures range from 6.5 °C (low) to 13.5 °C (high). Annual precipitation averages 2074.7 Millimeters. Sekiu is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 3.3 °C | 8.2 °C | 353.31 mm |
| February | 2.9 °C | 9.1 °C | 210.82 mm |
| March | 3.7 °C | 10.4 °C | 231.65 mm |
| April | 5 °C | 12.9 °C | 139.19 mm |
| May | 7.2 °C | 15.2 °C | 77.72 mm |
| June | 9.5 °C | 16.9 °C | 55.12 mm |
| July | 10.7 °C | 18.5 °C | 37.08 mm |
| August | 11 °C | 19 °C | 40.13 mm |
| September | 9.7 °C | 18.1 °C | 61.98 mm |
| October | 7.3 °C | 14.5 °C | 187.71 mm |
| November | 4.7 °C | 10.5 °C | 338.58 mm |
| December | 2.8 °C | 8.1 °C | 341.38 mm |
| Annual | 6.5 °C | 13.5 °C | 2074.67 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 50-75 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 | Cfb - Temperate Oceanic Climate |