Circle, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 30.7 °F (low) to 57.2 °F (high). Annual precipitation averages 14 Inches. 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 | 5.4 °F | 27.5 °F | 0.32 in. |
| February | 9.5 °F | 32.1 °F | 0.31 in. |
| March | 19.7 °F | 44.4 °F | 0.43 in. |
| April | 29.9 °F | 57.3 °F | 1.25 in. |
| May | 40.1 °F | 67.7 °F | 2.26 in. |
| June | 49.8 °F | 76.8 °F | 2.75 in. |
| July | 55.6 °F | 86.2 °F | 2.22 in. |
| August | 53.9 °F | 86.1 °F | 1.45 in. |
| September | 43.9 °F | 75.1 °F | 1.33 in. |
| October | 31.4 °F | 58.9 °F | 0.91 in. |
| November | 19.3 °F | 43.0 °F | 0.37 in. |
| December | 9.3 °F | 31.1 °F | 0.35 in. |
| Annual | 30.7 °F | 57.2 °F | 13.95 in. |
| 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 : -30°F to -25°F |
| Plant Hardiness Zone - 2012 | Zone 3b : -35°F to -30°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |