Fort Smith, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 36.2 °F (low) to 62.3 °F (high). Annual precipitation averages 16.8 Inches. Fort Smith is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 17.0 °F | 38.9 °F | 0.75 in. |
| February | 18.9 °F | 41.8 °F | 0.76 in. |
| March | 26.5 °F | 51.3 °F | 1.2 in. |
| April | 34.7 °F | 59.7 °F | 2.22 in. |
| May | 43.4 °F | 69.5 °F | 2.64 in. |
| June | 51.7 °F | 79.7 °F | 2.09 in. |
| July | 58.0 °F | 90.0 °F | 1.13 in. |
| August | 55.8 °F | 88.6 °F | 0.79 in. |
| September | 47.2 °F | 77.6 °F | 1.66 in. |
| October | 36.2 °F | 62.5 °F | 1.91 in. |
| November | 26.1 °F | 48.6 °F | 0.92 in. |
| December | 18.6 °F | 39.6 °F | 0.69 in. |
| Annual | 36.2 °F | 62.3 °F | 16.76 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |