Milton, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.5 °C (low) to 16.1 °C (high). Annual precipitation averages 1133.6 Millimeters. 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 | 1.9 °C | 8.4 °C | 161.29 mm |
| February | 1.9 °C | 9.9 °C | 105.66 mm |
| March | 3.2 °C | 12.2 °C | 122.68 mm |
| April | 5 °C | 15.2 °C | 92.2 mm |
| May | 8.1 °C | 19.1 °C | 57.66 mm |
| June | 10.5 °C | 21.5 °C | 49.78 mm |
| July | 12.5 °C | 25 °C | 21.08 mm |
| August | 12.6 °C | 25.3 °C | 31.5 mm |
| September | 10.3 °C | 22.1 °C | 45.47 mm |
| October | 6.8 °C | 16.1 °C | 113.54 mm |
| November | 3.8 °C | 11 °C | 168.4 mm |
| December | 1.7 °C | 7.9 °C | 164.34 mm |
| Annual | 6.5 °C | 16.1 °C | 1133.6 mm |
| 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 : -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 |