Harrisburg, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.7 °C (low) to 17.5 °C (high). Annual precipitation averages 1059.2 Millimeters. Harrisburg 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 Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.7 °C | 8.5 °C | 154.94 mm |
| February | 1.7 °C | 10.6 °C | 123.44 mm |
| March | 2.8 °C | 13.3 °C | 133.6 mm |
| April | 4.4 °C | 15.8 °C | 87.12 mm |
| May | 6.9 °C | 19.6 °C | 59.69 mm |
| June | 9.2 °C | 22.9 °C | 33.02 mm |
| July | 11.2 °C | 28 °C | 8.38 mm |
| August | 11.1 °C | 28.3 °C | 10.16 mm |
| September | 9 °C | 25.1 °C | 33.78 mm |
| October | 5.8 °C | 18 °C | 81.28 mm |
| November | 3.3 °C | 11.6 °C | 150.88 mm |
| December | 1.4 °C | 7.9 °C | 182.88 mm |
| Annual | 5.7 °C | 17.5 °C | 1059.17 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| 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 | Severe Drought |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |