Fairfield, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Annual precipitation averages 312.9 Millimeters. 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 | -9.2 °C | 2.2 °C | 8.38 mm |
| February | -9.1 °C | 2.9 °C | 8.89 mm |
| March | -5.4 °C | 7.2 °C | 15.49 mm |
| April | -1.2 °C | 12.1 °C | 37.08 mm |
| May | 3.6 °C | 17.1 °C | 52.07 mm |
| June | 7.6 °C | 21.4 °C | 65.53 mm |
| July | 10.7 °C | 27.3 °C | 27.69 mm |
| August | 9.9 °C | 26.9 °C | 27.69 mm |
| September | 5.7 °C | 21.2 °C | 31.24 mm |
| October | 0.6 °C | 13.7 °C | 18.03 mm |
| November | -4.4 °C | 6.5 °C | 11.68 mm |
| December | -8.6 °C | 2.3 °C | 9.14 mm |
| Annual | 0 °C | 13.4 °C | 312.91 mm |
| 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 : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |