Alder, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.9 °C (low) to 13.5 °C (high). Annual precipitation averages 283.2 Millimeters. 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 | -9.5 °C | 1.6 °C | 10.92 mm |
| February | -9 °C | 3.2 °C | 11.68 mm |
| March | -5.2 °C | 8.1 °C | 12.45 mm |
| April | -1.8 °C | 12.3 °C | 26.92 mm |
| May | 2.4 °C | 17.3 °C | 38.61 mm |
| June | 6.2 °C | 21.8 °C | 52.83 mm |
| July | 9.3 °C | 27.6 °C | 32.77 mm |
| August | 8.4 °C | 27 °C | 24.13 mm |
| September | 4.5 °C | 21.6 °C | 22.1 mm |
| October | -0.7 °C | 14.3 °C | 23.11 mm |
| November | -5.8 °C | 6.3 °C | 13.46 mm |
| December | -10.1 °C | 1 °C | 14.22 mm |
| Annual | -0.9 °C | 13.5 °C | 283.2 mm |
| 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 : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |