Sidney, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from -0.5 °C (low) to 13.3 °C (high). Annual precipitation averages 390.4 Millimeters. Sidney 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 | -15.1 °C | -3.9 °C | 11.68 mm |
| February | -13.2 °C | -1.3 °C | 8.89 mm |
| March | -7.2 °C | 5.7 °C | 16 mm |
| April | -0.8 °C | 14 °C | 30.23 mm |
| May | 5.3 °C | 19.9 °C | 57.66 mm |
| June | 10.9 °C | 24.8 °C | 69.6 mm |
| July | 13.9 °C | 29.4 °C | 65.53 mm |
| August | 12.4 °C | 29.2 °C | 37.85 mm |
| September | 6.9 °C | 23.5 °C | 38.1 mm |
| October | 0.4 °C | 14.3 °C | 28.45 mm |
| November | -6.8 °C | 5.2 °C | 13.97 mm |
| December | -12.6 °C | -1.8 °C | 12.45 mm |
| Annual | -0.5 °C | 13.3 °C | 390.41 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |