Milton, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 43.7 °F (low) to 61.1 °F (high). Annual precipitation averages 44.6 Inches. Milton is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 11 - Mar. 20 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 35.5 °F | 47.2 °F | 6.35 in. |
| February | 35.4 °F | 49.8 °F | 4.16 in. |
| March | 37.7 °F | 54.0 °F | 4.83 in. |
| April | 41.0 °F | 59.4 °F | 3.63 in. |
| May | 46.6 °F | 66.3 °F | 2.27 in. |
| June | 50.9 °F | 70.7 °F | 1.96 in. |
| July | 54.5 °F | 77.0 °F | 0.83 in. |
| August | 54.6 °F | 77.5 °F | 1.24 in. |
| September | 50.5 °F | 71.7 °F | 1.79 in. |
| October | 44.3 °F | 60.9 °F | 4.47 in. |
| November | 38.8 °F | 51.8 °F | 6.63 in. |
| December | 35.0 °F | 46.3 °F | 6.47 in. |
| Annual | 43.7 °F | 61.1 °F | 44.63 in. |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| Average Days With Frost | 30-40 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 |