Forest Grove, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.3 °C (low) to 17.2 °C (high). Annual precipitation averages 1119.9 Millimeters. Forest Grove 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 | 1.7 °C | 8.2 °C | 178.82 mm |
| February | 1.7 °C | 10.3 °C | 128.52 mm |
| March | 3.1 °C | 13.1 °C | 120.9 mm |
| April | 4.7 °C | 15.9 °C | 82.8 mm |
| May | 7.8 °C | 20.1 °C | 52.83 mm |
| June | 10.2 °C | 22.8 °C | 33.02 mm |
| July | 12.5 °C | 27.3 °C | 7.62 mm |
| August | 12.4 °C | 27.8 °C | 11.94 mm |
| September | 10 °C | 24.6 °C | 32.51 mm |
| October | 6.4 °C | 17.7 °C | 90.17 mm |
| November | 3.6 °C | 11.3 °C | 168.4 mm |
| December | 1.4 °C | 7.7 °C | 212.34 mm |
| Annual | 6.3 °C | 17.2 °C | 1119.87 mm |
| 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 : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |