Monroe, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 43.2 °F (low) to 60.3 °F (high). Annual precipitation averages 50.7 Inches. 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 | 34.9 °F | 46.7 °F | 6.52 in. |
| February | 34.9 °F | 49.7 °F | 4.52 in. |
| March | 37.3 °F | 53.7 °F | 5.24 in. |
| April | 41.0 °F | 58.8 °F | 4.37 in. |
| May | 46.2 °F | 65.4 °F | 3.23 in. |
| June | 50.5 °F | 69.5 °F | 2.65 in. |
| July | 53.5 °F | 75.6 °F | 1.18 in. |
| August | 53.5 °F | 76.5 °F | 1.18 in. |
| September | 49.7 °F | 70.8 °F | 2.67 in. |
| October | 43.7 °F | 60.0 °F | 4.87 in. |
| November | 38.3 °F | 51.3 °F | 7.34 in. |
| December | 34.6 °F | 45.8 °F | 6.97 in. |
| Annual | 43.2 °F | 60.3 °F | 50.74 in. |
| 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 : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |