Cornelius, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 43.6 °F (low) to 63.1 °F (high). Annual precipitation averages 42.4 Inches. Cornelius 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 | 35.3 °F | 46.9 °F | 6.66 in. |
| February | 35.3 °F | 50.8 °F | 4.78 in. |
| March | 37.8 °F | 55.6 °F | 4.55 in. |
| April | 40.8 °F | 60.9 °F | 3.13 in. |
| May | 46.4 °F | 68.2 °F | 2.07 in. |
| June | 50.7 °F | 73.3 °F | 1.32 in. |
| July | 54.7 °F | 81.3 °F | 0.31 in. |
| August | 54.5 °F | 82.1 °F | 0.48 in. |
| September | 50.2 °F | 76.2 °F | 1.28 in. |
| October | 43.8 °F | 63.9 °F | 3.44 in. |
| November | 38.6 °F | 52.5 °F | 6.38 in. |
| December | 34.8 °F | 46.0 °F | 7.97 in. |
| Annual | 43.6 °F | 63.1 °F | 42.37 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 |