Oak Harbor, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.9 °C (low) to 14.3 °C (high). Annual precipitation averages 625.9 Millimeters. 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 | 1.9 °C | 7.9 °C | 80.01 mm |
| February | 1.8 °C | 9 °C | 54.36 mm |
| March | 3.1 °C | 11.1 °C | 57.4 mm |
| April | 4.8 °C | 13.6 °C | 51.56 mm |
| May | 7.4 °C | 16.6 °C | 45.47 mm |
| June | 9.6 °C | 18.8 °C | 32.77 mm |
| July | 10.8 °C | 21.2 °C | 18.03 mm |
| August | 10.8 °C | 21.8 °C | 20.07 mm |
| September | 9.1 °C | 19.3 °C | 31.5 mm |
| October | 6.2 °C | 14.5 °C | 67.31 mm |
| November | 3.7 °C | 10.3 °C | 93.73 mm |
| December | 1.8 °C | 7.6 °C | 73.66 mm |
| Annual | 5.9 °C | 14.3 °C | 625.87 mm |
| 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 : -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 |