Farmington, Washington has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 2.2 °C (low) to 14.5 °C (high). Annual precipitation averages 614.4 Millimeters. Farmington is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -3.7 °C | 2.7 °C | 81.53 mm |
| February | -3.3 °C | 4.8 °C | 59.18 mm |
| March | -1.2 °C | 8.9 °C | 65.02 mm |
| April | 1.3 °C | 13.2 °C | 52.07 mm |
| May | 4.7 °C | 18.4 °C | 57.15 mm |
| June | 7.4 °C | 21.7 °C | 41.91 mm |
| July | 9.3 °C | 28 °C | 15.75 mm |
| August | 9.2 °C | 28.7 °C | 14.99 mm |
| September | 5.8 °C | 23.4 °C | 19.3 mm |
| October | 1.8 °C | 15.2 °C | 50.29 mm |
| November | -1.2 °C | 6.7 °C | 74.42 mm |
| December | -4.2 °C | 1.9 °C | 82.8 mm |
| Annual | 2.2 °C | 14.5 °C | 614.41 mm |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |