Chester, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from -1.5 °C (low) to 13.6 °C (high). Annual precipitation averages 291.3 Millimeters. Chester is located in USDA Plant Hardiness Zone 3b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep.1 - Sep. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -13.8 °C | -0.7 °C | 11.94 mm |
| February | -12.2 °C | 1.6 °C | 9.14 mm |
| March | -7.3 °C | 6.7 °C | 11.43 mm |
| April | -1.7 °C | 13.4 °C | 24.64 mm |
| May | 3.7 °C | 18.8 °C | 42.93 mm |
| June | 8.2 °C | 23.1 °C | 66.55 mm |
| July | 11.2 °C | 28.6 °C | 33.02 mm |
| August | 10.2 °C | 28.3 °C | 27.43 mm |
| September | 5.3 °C | 22.3 °C | 22.86 mm |
| October | -1.2 °C | 14.3 °C | 16.76 mm |
| November | -7.4 °C | 5.9 °C | 13.21 mm |
| December | -12.4 °C | 0.4 °C | 11.43 mm |
| Annual | -1.5 °C | 13.6 °C | 291.34 mm |
| Average First Frost Date | Sep.1 - Sep. 10 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 3b : -37.2°C to -34.4°C |
| Plant Hardiness Zone - 2012 | Zone 3b : -37.2°C to -34.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |