King Arthur Park, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.4 °C (low) to 13.7 °C (high). Annual precipitation averages 430.5 Millimeters. King Arthur Park is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.4 °C | 1.6 °C | 15.75 mm |
| February | -8.7 °C | 3 °C | 16 mm |
| March | -4.9 °C | 7.9 °C | 25.65 mm |
| April | -1.3 °C | 12.4 °C | 54.1 mm |
| May | 3.1 °C | 17.4 °C | 66.8 mm |
| June | 6.8 °C | 22.2 °C | 74.42 mm |
| July | 10.1 °C | 28.3 °C | 32.77 mm |
| August | 9.1 °C | 28.1 °C | 30.48 mm |
| September | 5.2 °C | 22.3 °C | 33.53 mm |
| October | -0.1 °C | 14.2 °C | 39.12 mm |
| November | -5.4 °C | 6.2 °C | 23.37 mm |
| December | -9.7 °C | 1.3 °C | 18.54 mm |
| Annual | -0.4 °C | 13.7 °C | 430.53 mm |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |