Frenchtown, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.1 °C (low) to 14.7 °C (high). Annual precipitation averages 349.3 Millimeters. 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 | -6.9 °C | 1.4 °C | 24.13 mm |
| February | -6 °C | 4.1 °C | 23.37 mm |
| March | -2.9 °C | 9.7 °C | 22.35 mm |
| April | 0.2 °C | 14.2 °C | 30.99 mm |
| May | 4.2 °C | 19.7 °C | 45.21 mm |
| June | 7.9 °C | 23.6 °C | 50.8 mm |
| July | 10.5 °C | 30 °C | 19.05 mm |
| August | 9.7 °C | 29.7 °C | 22.35 mm |
| September | 5.6 °C | 23.4 °C | 25.4 mm |
| October | 0.7 °C | 14.4 °C | 28.96 mm |
| November | -3.6 °C | 5.8 °C | 30.48 mm |
| December | -6.7 °C | 0.9 °C | 26.16 mm |
| Annual | 1.1 °C | 14.7 °C | 349.25 mm |
| 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 : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |