Portland, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 7.4 °C (low) to 17.3 °C (high). Annual precipitation averages 1094.5 Millimeters. Portland is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Feb. 21 - Feb. 29 through the first frost around Dec. 1 - Dec. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.4 °C | 8.3 °C | 163.32 mm |
| February | 2.7 °C | 10.4 °C | 114.81 mm |
| March | 4.1 °C | 13.3 °C | 117.86 mm |
| April | 5.9 °C | 16.2 °C | 89.41 mm |
| May | 8.9 °C | 20.2 °C | 61.47 mm |
| June | 11.3 °C | 22.8 °C | 41.66 mm |
| July | 13.6 °C | 27.1 °C | 10.67 mm |
| August | 13.6 °C | 27.6 °C | 13.72 mm |
| September | 11.2 °C | 24.3 °C | 37.85 mm |
| October | 7.7 °C | 17.8 °C | 93.47 mm |
| November | 4.7 °C | 11.7 °C | 162.31 mm |
| December | 2.3 °C | 8.1 °C | 187.96 mm |
| Annual | 7.4 °C | 17.3 °C | 1094.51 mm |
| Average First Frost Date | Dec. 1 - Dec. 10 |
| Average Last Frost Date | Feb. 21 - Feb. 29 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 9a : -6.7°C to -3.9°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |