Sultan, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.2 °C (low) to 16 °C (high). Annual precipitation averages 1425.5 Millimeters. Sultan 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 | 1.6 °C | 8.1 °C | 187.45 mm |
| February | 1.7 °C | 9.8 °C | 130.05 mm |
| March | 2.9 °C | 12.1 °C | 141.48 mm |
| April | 4.9 °C | 15.1 °C | 123.95 mm |
| May | 7.8 °C | 18.9 °C | 92.71 mm |
| June | 10.2 °C | 21.1 °C | 79.25 mm |
| July | 11.9 °C | 24.9 °C | 31.5 mm |
| August | 11.9 °C | 25.4 °C | 35.31 mm |
| September | 9.7 °C | 22.1 °C | 73.66 mm |
| October | 6.4 °C | 16.1 °C | 146.3 mm |
| November | 3.4 °C | 10.7 °C | 198.12 mm |
| December | 1.4 °C | 7.6 °C | 185.67 mm |
| Annual | 6.2 °C | 16 °C | 1425.45 mm |
| 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 : -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 |