Joliet, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.1 °C (low) to 15.7 °C (high). Annual precipitation averages 372.4 Millimeters. Joliet is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.1 °C | 2.9 °C | 14.22 mm |
| February | -9.1 °C | 4.6 °C | 14.99 mm |
| March | -4.8 °C | 10.3 °C | 22.1 mm |
| April | -0.8 °C | 14.5 °C | 46.48 mm |
| May | 4.3 °C | 19.6 °C | 68.58 mm |
| June | 8.7 °C | 24.9 °C | 54.86 mm |
| July | 11.9 °C | 30.6 °C | 24.89 mm |
| August | 10.7 °C | 29.9 °C | 21.34 mm |
| September | 5.9 °C | 24.1 °C | 32.51 mm |
| October | -0.1 °C | 15.7 °C | 40.39 mm |
| November | -5.3 °C | 8.3 °C | 17.27 mm |
| December | -9.9 °C | 2.8 °C | 14.73 mm |
| Annual | 0.1 °C | 15.7 °C | 372.36 mm |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |