Frenchtown, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 33.9 °F (low) to 58.5 °F (high). Annual precipitation averages 13.8 Inches. Frenchtown is located in USDA Plant Hardiness Zone 5b. 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 | 19.6 °F | 34.6 °F | 0.95 in. |
| February | 21.2 °F | 39.3 °F | 0.92 in. |
| March | 26.7 °F | 49.4 °F | 0.88 in. |
| April | 32.3 °F | 57.6 °F | 1.22 in. |
| May | 39.5 °F | 67.4 °F | 1.78 in. |
| June | 46.2 °F | 74.4 °F | 2.0 in. |
| July | 50.9 °F | 86.0 °F | 0.75 in. |
| August | 49.4 °F | 85.5 °F | 0.88 in. |
| September | 42.0 °F | 74.1 °F | 1.0 in. |
| October | 33.2 °F | 58.0 °F | 1.14 in. |
| November | 25.6 °F | 42.4 °F | 1.2 in. |
| December | 19.9 °F | 33.6 °F | 1.03 in. |
| Annual | 33.9 °F | 58.5 °F | 13.75 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 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |