Startup, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.1 °C (low) to 16 °C (high). Annual precipitation averages 1661.4 Millimeters. Startup is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.5 °C | 8 °C | 218.95 mm |
| February | 1.6 °C | 9.8 °C | 150.88 mm |
| March | 2.8 °C | 12.1 °C | 164.34 mm |
| April | 4.8 °C | 15.1 °C | 144.02 mm |
| May | 7.8 °C | 18.9 °C | 113.28 mm |
| June | 10.2 °C | 21.1 °C | 95.25 mm |
| July | 11.9 °C | 25 °C | 36.07 mm |
| August | 11.8 °C | 25.5 °C | 41.4 mm |
| September | 9.7 °C | 22.2 °C | 85.09 mm |
| October | 6.4 °C | 16.2 °C | 170.69 mm |
| November | 3.4 °C | 10.7 °C | 235.97 mm |
| December | 1.4 °C | 7.5 °C | 205.49 mm |
| Annual | 6.1 °C | 16 °C | 1661.43 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 |