Cromwell, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 29.5 °F (low) to 50.3 °F (high). Annual precipitation averages 30.5 Inches. Cromwell is located in USDA Plant Hardiness Zone 4a. 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 | -0.2 °F | 18.9 °F | 0.79 in. |
| February | 2.9 °F | 24.8 °F | 0.79 in. |
| March | 15.3 °F | 37.0 °F | 1.29 in. |
| April | 28.4 °F | 50.2 °F | 2.34 in. |
| May | 40.1 °F | 64.0 °F | 3.49 in. |
| June | 49.9 °F | 73.0 °F | 4.54 in. |
| July | 55.0 °F | 77.7 °F | 4.48 in. |
| August | 53.3 °F | 76.0 °F | 3.79 in. |
| September | 45.6 °F | 67.9 °F | 3.31 in. |
| October | 34.3 °F | 53.1 °F | 3.04 in. |
| November | 21.5 °F | 37.1 °F | 1.48 in. |
| December | 8.0 °F | 24.0 °F | 1.14 in. |
| Annual | 29.5 °F | 50.3 °F | 30.48 in. |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 4a : -30°F to -25°F |
| Plant Hardiness Zone - 2012 | Zone 3b : -35°F to -30°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |