Oak Harbor, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 42.7 °F (low) to 57.7 °F (high). Annual precipitation averages 24.6 Inches. Oak Harbor is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 35.5 °F | 46.3 °F | 3.15 in. |
| February | 35.3 °F | 48.2 °F | 2.14 in. |
| March | 37.6 °F | 52.0 °F | 2.26 in. |
| April | 40.7 °F | 56.4 °F | 2.03 in. |
| May | 45.3 °F | 61.8 °F | 1.79 in. |
| June | 49.2 °F | 65.8 °F | 1.29 in. |
| July | 51.5 °F | 70.2 °F | 0.71 in. |
| August | 51.5 °F | 71.2 °F | 0.79 in. |
| September | 48.3 °F | 66.7 °F | 1.24 in. |
| October | 43.1 °F | 58.1 °F | 2.65 in. |
| November | 38.7 °F | 50.6 °F | 3.69 in. |
| December | 35.3 °F | 45.6 °F | 2.9 in. |
| Annual | 42.7 °F | 57.7 °F | 24.64 in. |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 40-50 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 |