Alder, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 30.3 °F (low) to 56.3 °F (high). Annual precipitation averages 11.2 Inches. Alder 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.1 - Sep. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 14.9 °F | 34.9 °F | 0.43 in. |
| February | 15.8 °F | 37.8 °F | 0.46 in. |
| March | 22.7 °F | 46.6 °F | 0.49 in. |
| April | 28.8 °F | 54.2 °F | 1.06 in. |
| May | 36.4 °F | 63.1 °F | 1.52 in. |
| June | 43.1 °F | 71.2 °F | 2.08 in. |
| July | 48.7 °F | 81.6 °F | 1.29 in. |
| August | 47.2 °F | 80.6 °F | 0.95 in. |
| September | 40.1 °F | 70.8 °F | 0.87 in. |
| October | 30.7 °F | 57.7 °F | 0.91 in. |
| November | 21.5 °F | 43.4 °F | 0.53 in. |
| December | 13.9 °F | 33.8 °F | 0.56 in. |
| Annual | 30.3 °F | 56.3 °F | 11.15 in. |
| Average First Frost Date | Sep.1 - Sep. 10 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |