Lewisville, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 42.1 °F (low) to 61.6 °F (high). Annual precipitation averages 55.1 Inches. Lewisville is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 33.6 °F | 45.6 °F | 7.6 in. |
| February | 33.7 °F | 49.7 °F | 5.54 in. |
| March | 36.3 °F | 54.4 °F | 6.0 in. |
| April | 39.6 °F | 59.6 °F | 4.73 in. |
| May | 45.1 °F | 66.7 °F | 3.52 in. |
| June | 49.2 °F | 71.1 °F | 2.45 in. |
| July | 53.0 °F | 78.5 °F | 0.67 in. |
| August | 52.9 °F | 79.8 °F | 0.82 in. |
| September | 48.5 °F | 74.4 °F | 2.31 in. |
| October | 42.4 °F | 62.8 °F | 5.11 in. |
| November | 37.3 °F | 51.6 °F | 7.92 in. |
| December | 33.4 °F | 44.9 °F | 8.4 in. |
| Annual | 42.1 °F | 61.6 °F | 55.07 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8b : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8a : 10°F to 15°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |