Ronan, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.2 °C (low) to 13.8 °C (high). Annual precipitation averages 432.3 Millimeters. Ronan is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.3 °C | 1.3 °C | 32.77 mm |
| February | -6.2 °C | 3.3 °C | 26.67 mm |
| March | -3.1 °C | 8.7 °C | 28.7 mm |
| April | 0.3 °C | 13.1 °C | 42.42 mm |
| May | 4.2 °C | 18.4 °C | 52.32 mm |
| June | 7.8 °C | 22.2 °C | 69.34 mm |
| July | 10.6 °C | 28.5 °C | 23.62 mm |
| August | 9.9 °C | 28.3 °C | 21.34 mm |
| September | 6 °C | 22.1 °C | 33.02 mm |
| October | 1.1 °C | 13.4 °C | 37.85 mm |
| November | -3.2 °C | 5.4 °C | 33.02 mm |
| December | -6.2 °C | 0.9 °C | 31.24 mm |
| Annual | 1.2 °C | 13.8 °C | 432.31 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |