Startup, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 43 °F (low) to 60.8 °F (high). Annual precipitation averages 65.4 Inches. 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 | 34.7 °F | 46.4 °F | 8.62 in. |
| February | 34.9 °F | 49.6 °F | 5.94 in. |
| March | 37.1 °F | 53.8 °F | 6.47 in. |
| April | 40.7 °F | 59.2 °F | 5.67 in. |
| May | 46.0 °F | 66.1 °F | 4.46 in. |
| June | 50.3 °F | 70.0 °F | 3.75 in. |
| July | 53.4 °F | 77.0 °F | 1.42 in. |
| August | 53.3 °F | 77.9 °F | 1.63 in. |
| September | 49.4 °F | 72.0 °F | 3.35 in. |
| October | 43.5 °F | 61.2 °F | 6.72 in. |
| November | 38.1 °F | 51.2 °F | 9.29 in. |
| December | 34.5 °F | 45.5 °F | 8.09 in. |
| Annual | 43 °F | 60.8 °F | 65.41 in. |
| 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 : 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 |