Joliet, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 32.2 °F (low) to 60.2 °F (high). Annual precipitation averages 14.7 Inches. 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 | 13.8 °F | 37.2 °F | 0.56 in. |
| February | 15.6 °F | 40.2 °F | 0.59 in. |
| March | 23.3 °F | 50.5 °F | 0.87 in. |
| April | 30.6 °F | 58.1 °F | 1.83 in. |
| May | 39.7 °F | 67.3 °F | 2.7 in. |
| June | 47.7 °F | 76.9 °F | 2.16 in. |
| July | 53.5 °F | 87.0 °F | 0.98 in. |
| August | 51.2 °F | 85.9 °F | 0.84 in. |
| September | 42.7 °F | 75.3 °F | 1.28 in. |
| October | 31.9 °F | 60.2 °F | 1.59 in. |
| November | 22.5 °F | 47.0 °F | 0.68 in. |
| December | 14.1 °F | 37.1 °F | 0.58 in. |
| Annual | 32.2 °F | 60.2 °F | 14.66 in. |
| 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 : -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 |