Sultan, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 43.1 °F (low) to 60.8 °F (high). Annual precipitation averages 56.1 Inches. 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 | 34.8 °F | 46.5 °F | 7.38 in. |
| February | 35.0 °F | 49.7 °F | 5.12 in. |
| March | 37.2 °F | 53.8 °F | 5.57 in. |
| April | 40.8 °F | 59.2 °F | 4.88 in. |
| May | 46.0 °F | 66.0 °F | 3.65 in. |
| June | 50.4 °F | 70.0 °F | 3.12 in. |
| July | 53.5 °F | 76.8 °F | 1.24 in. |
| August | 53.4 °F | 77.7 °F | 1.39 in. |
| September | 49.5 °F | 71.8 °F | 2.9 in. |
| October | 43.5 °F | 61.0 °F | 5.76 in. |
| November | 38.2 °F | 51.2 °F | 7.8 in. |
| December | 34.6 °F | 45.6 °F | 7.31 in. |
| Annual | 43.1 °F | 60.8 °F | 56.12 in. |
| 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 : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |