Fairfield, Washington has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 35.8 °F (low) to 57.9 °F (high). Annual precipitation averages 22 Inches. Fairfield is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 24.4 °F | 36.1 °F | 2.74 in. |
| February | 25.3 °F | 40.0 °F | 1.98 in. |
| March | 29.3 °F | 47.9 °F | 2.37 in. |
| April | 34.0 °F | 55.9 °F | 1.83 in. |
| May | 40.5 °F | 65.2 °F | 2.07 in. |
| June | 45.8 °F | 71.4 °F | 1.68 in. |
| July | 50.2 °F | 83.0 °F | 0.61 in. |
| August | 50.1 °F | 83.7 °F | 0.54 in. |
| September | 42.8 °F | 73.9 °F | 0.74 in. |
| October | 34.8 °F | 58.9 °F | 1.8 in. |
| November | 29.1 °F | 43.6 °F | 2.72 in. |
| December | 23.8 °F | 34.8 °F | 2.94 in. |
| Annual | 35.8 °F | 57.9 °F | 22.02 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |