Brockton, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from -1.6 °C (low) to 13.2 °C (high). Annual precipitation averages 362.2 Millimeters. Brockton is located in USDA Plant Hardiness Zone 4a. 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 | -16.8 °C | -4.8 °C | 8.13 mm |
| February | -14.7 °C | -1.8 °C | 7.11 mm |
| March | -8.1 °C | 5.4 °C | 12.95 mm |
| April | -1.6 °C | 14.1 °C | 26.16 mm |
| May | 4.4 °C | 20.4 °C | 56.39 mm |
| June | 10.3 °C | 25.4 °C | 75.18 mm |
| July | 12.9 °C | 29.8 °C | 65.02 mm |
| August | 11.7 °C | 29.8 °C | 37.34 mm |
| September | 6.1 °C | 23.8 °C | 31.24 mm |
| October | -0.9 °C | 14.5 °C | 21.84 mm |
| November | -8.2 °C | 4.7 °C | 11.43 mm |
| December | -14.3 °C | -2.4 °C | 9.4 mm |
| Annual | -1.6 °C | 13.2 °C | 362.19 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 3b : -37.2°C to -34.4°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |