Lengby, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 28.7 °F (low) to 49.7 °F (high). Annual precipitation averages 25.7 Inches. Lengby is located in USDA Plant Hardiness Zone 3b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -3.6 °F | 16.5 °F | 0.77 in. |
| February | -0.9 °F | 21.6 °F | 0.68 in. |
| March | 13.7 °F | 34.8 °F | 0.95 in. |
| April | 28.3 °F | 50.6 °F | 1.45 in. |
| May | 41.6 °F | 64.8 °F | 3.09 in. |
| June | 52.6 °F | 73.9 °F | 4.68 in. |
| July | 56.4 °F | 78.7 °F | 3.82 in. |
| August | 53.8 °F | 77.1 °F | 2.97 in. |
| September | 45.2 °F | 68.3 °F | 2.97 in. |
| October | 33.5 °F | 52.6 °F | 2.4 in. |
| November | 19.0 °F | 35.2 °F | 0.98 in. |
| December | 4.9 °F | 22.1 °F | 0.92 in. |
| Annual | 28.7 °F | 49.7 °F | 25.68 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 3b : -35°F to -30°F |
| Plant Hardiness Zone - 2012 | Zone 3b : -35°F to -30°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |