Opheim, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from -2.4 °C (low) to 9.9 °C (high). Annual precipitation averages 354.8 Millimeters. Opheim is located in USDA Plant Hardiness Zone 4a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep.1 - Sep. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -16.2 °C | -6.4 °C | 8.64 mm |
| February | -14.7 °C | -4.6 °C | 7.87 mm |
| March | -9.2 °C | 2 °C | 13.21 mm |
| April | -2.9 °C | 10.4 °C | 23.62 mm |
| May | 3.1 °C | 16.9 °C | 50.04 mm |
| June | 8.2 °C | 21.3 °C | 81.28 mm |
| July | 11.1 °C | 25.9 °C | 55.88 mm |
| August | 10.4 °C | 26 °C | 33.53 mm |
| September | 5.2 °C | 19.8 °C | 34.29 mm |
| October | -1.3 °C | 10.9 °C | 21.08 mm |
| November | -8.7 °C | 1.8 °C | 15.49 mm |
| December | -14.3 °C | -4.8 °C | 9.91 mm |
| Annual | -2.4 °C | 9.9 °C | 354.84 mm |
| Average First Frost Date | Sep.1 - Sep. 10 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 3b : -37.2°C to -34.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |