Circle, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from -0.8 °C (low) to 14 °C (high). Annual precipitation averages 354.3 Millimeters. Circle is located in USDA Plant Hardiness Zone 4a. 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 | -14.8 °C | -2.5 °C | 8.13 mm |
| February | -12.5 °C | 0.1 °C | 7.87 mm |
| March | -6.8 °C | 6.9 °C | 10.92 mm |
| April | -1.2 °C | 14.1 °C | 31.75 mm |
| May | 4.5 °C | 19.8 °C | 57.4 mm |
| June | 9.9 °C | 24.9 °C | 69.85 mm |
| July | 13.1 °C | 30.1 °C | 56.39 mm |
| August | 12.2 °C | 30.1 °C | 36.83 mm |
| September | 6.6 °C | 23.9 °C | 33.78 mm |
| October | -0.3 °C | 14.9 °C | 23.11 mm |
| November | -7.1 °C | 6.1 °C | 9.4 mm |
| December | -12.6 °C | -0.5 °C | 8.89 mm |
| Annual | -0.8 °C | 14 °C | 354.32 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| 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 | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |