Happy Valley, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.2 °C (low) to 16.9 °C (high). Annual precipitation averages 1254 Millimeters. Happy Valley is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.7 °C | 7.7 °C | 170.18 mm |
| February | 1.9 °C | 9.7 °C | 121.67 mm |
| March | 3.1 °C | 12.4 °C | 140.46 mm |
| April | 4.7 °C | 15.7 °C | 104.9 mm |
| May | 7.4 °C | 19.9 °C | 88.14 mm |
| June | 9.8 °C | 22.7 °C | 58.67 mm |
| July | 11.8 °C | 27.2 °C | 15.49 mm |
| August | 12.1 °C | 27.6 °C | 14.48 mm |
| September | 10.1 °C | 24.1 °C | 50.04 mm |
| October | 6.9 °C | 17.2 °C | 120.4 mm |
| November | 3.9 °C | 10.9 °C | 179.58 mm |
| December | 1.5 °C | 7.3 °C | 189.99 mm |
| Annual | 6.2 °C | 16.9 °C | 1254 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 30-40 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 |