Hillsboro, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 43.7 °F (low) to 63.2 °F (high). Annual precipitation averages 39.8 Inches. Hillsboro is located in USDA Plant Hardiness Zone 8b. 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 | 35.4 °F | 47.0 °F | 6.08 in. |
| February | 35.5 °F | 50.9 °F | 4.24 in. |
| March | 37.9 °F | 55.8 °F | 4.1 in. |
| April | 41.0 °F | 61.0 °F | 2.89 in. |
| May | 46.6 °F | 68.3 °F | 2.13 in. |
| June | 50.8 °F | 73.4 °F | 1.41 in. |
| July | 54.8 °F | 81.3 °F | 0.34 in. |
| August | 54.7 °F | 82.1 °F | 0.53 in. |
| September | 50.3 °F | 76.2 °F | 1.28 in. |
| October | 43.9 °F | 63.9 °F | 3.32 in. |
| November | 38.7 °F | 52.6 °F | 5.99 in. |
| December | 34.9 °F | 46.1 °F | 7.45 in. |
| Annual | 43.7 °F | 63.2 °F | 39.76 in. |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| 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 |