Cromwell, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -1.4 °C (low) to 10.2 °C (high). Annual precipitation averages 774.2 Millimeters. 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 | -17.9 °C | -7.3 °C | 20.07 mm |
| February | -16.2 °C | -4 °C | 20.07 mm |
| March | -9.3 °C | 2.8 °C | 32.77 mm |
| April | -2 °C | 10.1 °C | 59.44 mm |
| May | 4.5 °C | 17.8 °C | 88.65 mm |
| June | 9.9 °C | 22.8 °C | 115.32 mm |
| July | 12.8 °C | 25.4 °C | 113.79 mm |
| August | 11.8 °C | 24.4 °C | 96.27 mm |
| September | 7.6 °C | 19.9 °C | 84.07 mm |
| October | 1.3 °C | 11.7 °C | 77.22 mm |
| November | -5.8 °C | 2.8 °C | 37.59 mm |
| December | -13.3 °C | -4.4 °C | 28.96 mm |
| Annual | -1.4 °C | 10.2 °C | 774.22 mm |
| 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 : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 3b : -37.2°C to -34.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |