Fromberg, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 32.5 °F (low) to 60.7 °F (high). Annual precipitation averages 12.9 Inches. Fromberg 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. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 13.7 °F | 37.0 °F | 0.32 in. |
| February | 15.5 °F | 40.3 °F | 0.48 in. |
| March | 23.4 °F | 51.2 °F | 0.62 in. |
| April | 31.1 °F | 58.8 °F | 1.71 in. |
| May | 40.3 °F | 68.1 °F | 2.48 in. |
| June | 48.2 °F | 77.7 °F | 1.93 in. |
| July | 54.0 °F | 88.0 °F | 0.92 in. |
| August | 51.5 °F | 86.6 °F | 0.79 in. |
| September | 43.1 °F | 75.9 °F | 1.22 in. |
| October | 32.2 °F | 60.7 °F | 1.35 in. |
| November | 22.6 °F | 47.2 °F | 0.59 in. |
| December | 14.3 °F | 37.1 °F | 0.53 in. |
| Annual | 32.5 °F | 60.7 °F | 12.94 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 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |