Fairfield, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 32 °F (low) to 56.2 °F (high). Annual precipitation averages 12.3 Inches. Fairfield is located in USDA Plant Hardiness Zone 4b. 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 | 15.4 °F | 36.0 °F | 0.33 in. |
| February | 15.7 °F | 37.3 °F | 0.35 in. |
| March | 22.2 °F | 44.9 °F | 0.61 in. |
| April | 29.9 °F | 53.7 °F | 1.46 in. |
| May | 38.4 °F | 62.8 °F | 2.05 in. |
| June | 45.7 °F | 70.6 °F | 2.58 in. |
| July | 51.2 °F | 81.2 °F | 1.09 in. |
| August | 49.8 °F | 80.5 °F | 1.09 in. |
| September | 42.3 °F | 70.2 °F | 1.23 in. |
| October | 33.0 °F | 56.7 °F | 0.71 in. |
| November | 24.0 °F | 43.7 °F | 0.46 in. |
| December | 16.6 °F | 36.2 °F | 0.36 in. |
| Annual | 32 °F | 56.2 °F | 12.32 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 4b : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |