Amboy, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 42.1 °F (low) to 61.3 °F (high). Annual precipitation averages 65.4 Inches. 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 | 33.3 °F | 45.0 °F | 9.29 in. |
| February | 33.4 °F | 49.0 °F | 6.89 in. |
| March | 36.3 °F | 53.9 °F | 7.29 in. |
| April | 39.8 °F | 59.1 °F | 5.53 in. |
| May | 45.4 °F | 67.5 °F | 3.84 in. |
| June | 49.2 °F | 70.7 °F | 2.69 in. |
| July | 53.1 °F | 78.5 °F | 0.73 in. |
| August | 53.0 °F | 79.6 °F | 0.98 in. |
| September | 49.2 °F | 74.4 °F | 2.64 in. |
| October | 42.5 °F | 62.6 °F | 5.96 in. |
| November | 37.2 °F | 51.5 °F | 9.43 in. |
| December | 33.2 °F | 44.3 °F | 10.13 in. |
| Annual | 42.1 °F | 61.3 °F | 65.4 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 | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |