Sedro-Woolley, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6 °C (low) to 15.4 °C (high). Annual precipitation averages 1184.7 Millimeters. Sedro-Woolley 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 Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.7 °C | 8 °C | 150.62 mm |
| February | 1.6 °C | 9.2 °C | 100.33 mm |
| March | 3.1 °C | 11.4 °C | 118.11 mm |
| April | 4.9 °C | 14.6 °C | 102.87 mm |
| May | 7.6 °C | 18.3 °C | 80.77 mm |
| June | 9.9 °C | 20.6 °C | 64.77 mm |
| July | 11.3 °C | 23.7 °C | 30.99 mm |
| August | 11.2 °C | 24.2 °C | 36.83 mm |
| September | 9.2 °C | 20.9 °C | 71.12 mm |
| October | 6 °C | 15.5 °C | 119.89 mm |
| November | 3.5 °C | 10.6 °C | 177.29 mm |
| December | 1.4 °C | 7.4 °C | 131.06 mm |
| Annual | 6 °C | 15.4 °C | 1184.65 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |