Monroe, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.2 °C (low) to 15.7 °C (high). Annual precipitation averages 1288.8 Millimeters. Monroe 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 | 1.6 °C | 8.2 °C | 165.61 mm |
| February | 1.6 °C | 9.8 °C | 114.81 mm |
| March | 2.9 °C | 12.1 °C | 133.1 mm |
| April | 5 °C | 14.9 °C | 111 mm |
| May | 7.9 °C | 18.6 °C | 82.04 mm |
| June | 10.3 °C | 20.8 °C | 67.31 mm |
| July | 11.9 °C | 24.2 °C | 29.97 mm |
| August | 11.9 °C | 24.7 °C | 29.97 mm |
| September | 9.8 °C | 21.6 °C | 67.82 mm |
| October | 6.5 °C | 15.6 °C | 123.7 mm |
| November | 3.5 °C | 10.7 °C | 186.44 mm |
| December | 1.4 °C | 7.7 °C | 177.04 mm |
| Annual | 6.2 °C | 15.7 °C | 1288.81 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 | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |