River Road, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6 °C (low) to 14.7 °C (high). Annual precipitation averages 522.2 Millimeters. River Road is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.8 °C | 7.4 °C | 66.04 mm |
| February | 1.7 °C | 8.5 °C | 51.56 mm |
| March | 2.7 °C | 10.7 °C | 49.78 mm |
| April | 4.6 °C | 14.6 °C | 38.61 mm |
| May | 7.2 °C | 18.1 °C | 34.54 mm |
| June | 9.4 °C | 19.7 °C | 29.21 mm |
| July | 11.3 °C | 22.2 °C | 16.76 mm |
| August | 11.4 °C | 22.6 °C | 15.49 mm |
| September | 9.8 °C | 20.1 °C | 24.64 mm |
| October | 6.5 °C | 15.7 °C | 47.24 mm |
| November | 3.5 °C | 9.9 °C | 77.98 mm |
| December | 1.6 °C | 7.3 °C | 70.36 mm |
| Annual | 6 °C | 14.7 °C | 522.21 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°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 |