Curlew, Washington has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 34.2 °F (low) to 58.3 °F (high). Annual precipitation averages 18.9 Inches. Curlew is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 19.8 °F | 30.7 °F | 1.97 in. |
| February | 21.4 °F | 38.1 °F | 1.32 in. |
| March | 27.2 °F | 49.6 °F | 1.48 in. |
| April | 32.4 °F | 60.0 °F | 1.47 in. |
| May | 40.4 °F | 69.9 °F | 2.25 in. |
| June | 46.5 °F | 75.1 °F | 2.39 in. |
| July | 50.5 °F | 84.8 °F | 1.18 in. |
| August | 49.6 °F | 85.3 °F | 0.7 in. |
| September | 42.5 °F | 75.4 °F | 0.88 in. |
| October | 33.7 °F | 58.0 °F | 1.32 in. |
| November | 26.5 °F | 41.0 °F | 1.83 in. |
| December | 20.2 °F | 31.4 °F | 2.12 in. |
| Annual | 34.2 °F | 58.3 °F | 18.91 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |