Harrington, Washington has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 35.6 °F (low) to 58.6 °F (high). Annual precipitation averages 12.7 Inches. Harrington is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Aug. 21 - Aug. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 23.0 °F | 34.0 °F | 1.62 in. |
| February | 24.9 °F | 39.8 °F | 1.07 in. |
| March | 29.3 °F | 49.4 °F | 1.33 in. |
| April | 33.1 °F | 58.1 °F | 0.98 in. |
| May | 40.4 °F | 67.4 °F | 1.13 in. |
| June | 45.6 °F | 73.9 °F | 0.99 in. |
| July | 51.3 °F | 84.5 °F | 0.4 in. |
| August | 51.2 °F | 84.1 °F | 0.35 in. |
| September | 43.6 °F | 74.9 °F | 0.4 in. |
| October | 34.9 °F | 59.5 °F | 1.07 in. |
| November | 27.9 °F | 43.5 °F | 1.57 in. |
| December | 22.5 °F | 33.7 °F | 1.8 in. |
| Annual | 35.6 °F | 58.6 °F | 12.71 in. |
| Average First Frost Date | Aug. 21 - Aug. 31 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |