Mill City, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.4 °C (low) to 16.3 °C (high). Annual precipitation averages 1660.7 Millimeters. Mill City 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 | 0.9 °C | 7.8 °C | 214.63 mm |
| February | 1.2 °C | 9.6 °C | 168.66 mm |
| March | 2.4 °C | 12 °C | 192.28 mm |
| April | 4.1 °C | 14.8 °C | 162.56 mm |
| May | 6.7 °C | 18.6 °C | 115.82 mm |
| June | 9.3 °C | 21.8 °C | 73.15 mm |
| July | 11.3 °C | 26.5 °C | 14.99 mm |
| August | 11.2 °C | 27.1 °C | 18.03 mm |
| September | 8.7 °C | 23.4 °C | 64.01 mm |
| October | 5.8 °C | 16.6 °C | 143.76 mm |
| November | 2.9 °C | 10.3 °C | 231.39 mm |
| December | 0.8 °C | 7.1 °C | 261.37 mm |
| Annual | 5.4 °C | 16.3 °C | 1660.65 mm |
| 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 : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |