Amboy, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.6 °C (low) to 16.3 °C (high). Annual precipitation averages 1661.2 Millimeters. Amboy 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 | 0.7 °C | 7.2 °C | 235.97 mm |
| February | 0.8 °C | 9.4 °C | 175.01 mm |
| March | 2.4 °C | 12.2 °C | 185.17 mm |
| April | 4.3 °C | 15.1 °C | 140.46 mm |
| May | 7.4 °C | 19.7 °C | 97.54 mm |
| June | 9.6 °C | 21.5 °C | 68.33 mm |
| July | 11.7 °C | 25.8 °C | 18.54 mm |
| August | 11.7 °C | 26.4 °C | 24.89 mm |
| September | 9.6 °C | 23.6 °C | 67.06 mm |
| October | 5.8 °C | 17 °C | 151.38 mm |
| November | 2.9 °C | 10.8 °C | 239.52 mm |
| December | 0.7 °C | 6.8 °C | 257.3 mm |
| Annual | 5.6 °C | 16.3 °C | 1661.17 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 | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |