River Road, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 42.7 °F (low) to 58.5 °F (high). Annual precipitation averages 20.6 Inches. 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 | 35.2 °F | 45.4 °F | 2.6 in. |
| February | 35.1 °F | 47.3 °F | 2.03 in. |
| March | 36.8 °F | 51.2 °F | 1.96 in. |
| April | 40.2 °F | 58.2 °F | 1.52 in. |
| May | 44.9 °F | 64.5 °F | 1.36 in. |
| June | 49.0 °F | 67.5 °F | 1.15 in. |
| July | 52.4 °F | 72.0 °F | 0.66 in. |
| August | 52.5 °F | 72.7 °F | 0.61 in. |
| September | 49.6 °F | 68.2 °F | 0.97 in. |
| October | 43.7 °F | 60.2 °F | 1.86 in. |
| November | 38.3 °F | 49.8 °F | 3.07 in. |
| December | 34.9 °F | 45.1 °F | 2.77 in. |
| Annual | 42.7 °F | 58.5 °F | 20.56 in. |
| 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 : 10°F to 15°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |