Basin, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -3.2 °C (low) to 12.1 °C (high). Annual precipitation averages 385.3 Millimeters. Basin is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Aug. 21 - Aug. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12.2 °C | 0.7 °C | 22.61 mm |
| February | -11.1 °C | 2.2 °C | 18.29 mm |
| March | -7.2 °C | 6.5 °C | 25.15 mm |
| April | -3.7 °C | 10.4 °C | 32.26 mm |
| May | 0.4 °C | 15.6 °C | 46.99 mm |
| June | 4.1 °C | 20.2 °C | 67.82 mm |
| July | 7.1 °C | 26.5 °C | 41.4 mm |
| August | 6.1 °C | 26.1 °C | 36.07 mm |
| September | 2.2 °C | 20.2 °C | 27.18 mm |
| October | -2.9 °C | 12.3 °C | 22.86 mm |
| November | -8.4 °C | 4.8 °C | 21.08 mm |
| December | -12.6 °C | -0.1 °C | 23.62 mm |
| Annual | -3.2 °C | 12.1 °C | 385.33 mm |
| Average First Frost Date | Aug. 21 - Aug. 31 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 4b : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |