Willamina, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 42.7 °F (low) to 63.6 °F (high). Annual precipitation averages 48.2 Inches. Willamina 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. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 35.3 °F | 47.0 °F | 7.69 in. |
| February | 35.5 °F | 50.8 °F | 5.75 in. |
| March | 37.5 °F | 55.3 °F | 5.25 in. |
| April | 40.0 °F | 60.9 °F | 3.79 in. |
| May | 44.8 °F | 68.4 °F | 2.11 in. |
| June | 48.8 °F | 73.9 °F | 1.2 in. |
| July | 52.3 °F | 82.8 °F | 0.26 in. |
| August | 52.4 °F | 83.7 °F | 0.35 in. |
| September | 49.1 °F | 77.2 °F | 1.47 in. |
| October | 43.5 °F | 64.0 °F | 3.79 in. |
| November | 38.6 °F | 52.6 °F | 7.4 in. |
| December | 34.8 °F | 46.2 °F | 9.17 in. |
| Annual | 42.7 °F | 63.6 °F | 48.23 in. |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| 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 |