King Arthur Park, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 31.2 °F (low) to 56.8 °F (high). Annual precipitation averages 17 Inches. 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 | 15.0 °F | 34.8 °F | 0.62 in. |
| February | 16.3 °F | 37.4 °F | 0.63 in. |
| March | 23.1 °F | 46.3 °F | 1.01 in. |
| April | 29.6 °F | 54.4 °F | 2.13 in. |
| May | 37.5 °F | 63.4 °F | 2.63 in. |
| June | 44.3 °F | 72.0 °F | 2.93 in. |
| July | 50.1 °F | 83.0 °F | 1.29 in. |
| August | 48.3 °F | 82.5 °F | 1.2 in. |
| September | 41.4 °F | 72.2 °F | 1.32 in. |
| October | 31.8 °F | 57.6 °F | 1.54 in. |
| November | 22.2 °F | 43.2 °F | 0.92 in. |
| December | 14.6 °F | 34.3 °F | 0.73 in. |
| Annual | 31.2 °F | 56.8 °F | 16.95 in. |
| 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 : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |