Ilwaco, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 45.1 °F (low) to 58 °F (high). Annual precipitation averages 79.8 Inches. Ilwaco is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 38.8 °F | 49.1 °F | 12.2 in. |
| February | 38.6 °F | 50.8 °F | 7.95 in. |
| March | 40.2 °F | 53.1 °F | 8.78 in. |
| April | 41.7 °F | 55.7 °F | 6.64 in. |
| May | 46.5 °F | 59.9 °F | 3.84 in. |
| June | 49.7 °F | 62.9 °F | 2.71 in. |
| July | 53.9 °F | 66.2 °F | 1.05 in. |
| August | 53.5 °F | 67.6 °F | 1.58 in. |
| September | 51.4 °F | 67.2 °F | 2.7 in. |
| October | 46.3 °F | 61.0 °F | 7.64 in. |
| November | 42.7 °F | 53.6 °F | 12.12 in. |
| December | 38.4 °F | 48.6 °F | 12.57 in. |
| Annual | 45.1 °F | 58 °F | 79.78 in. |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 20-30 Days |
| Plant Hardiness Zone | Zone 9a : 20°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |