Roberts, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.6 °C (low) to 14.4 °C (high). Annual precipitation averages 373.4 Millimeters. Roberts is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.8 °C | 2.9 °C | 10.16 mm |
| February | -8.6 °C | 3.7 °C | 12.45 mm |
| March | -4.6 °C | 8.8 °C | 20.32 mm |
| April | -0.7 °C | 12.8 °C | 43.94 mm |
| May | 4.1 °C | 17.8 °C | 78.74 mm |
| June | 8.4 °C | 23.2 °C | 56.64 mm |
| July | 12.2 °C | 28.8 °C | 26.92 mm |
| August | 11.3 °C | 28.3 °C | 21.59 mm |
| September | 6.5 °C | 22.5 °C | 35.56 mm |
| October | 0.6 °C | 14.4 °C | 39.62 mm |
| November | -4.6 °C | 7.4 °C | 16 mm |
| December | -8.7 °C | 2.6 °C | 11.43 mm |
| Annual | 0.6 °C | 14.4 °C | 373.37 mm |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |