Winthrop, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.6 °C (low) to 12.4 °C (high). Annual precipitation averages 780.3 Millimeters. Winthrop is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -15.1 °C | -5.7 °C | 20.57 mm |
| February | -13.1 °C | -2.9 °C | 21.34 mm |
| March | -6 °C | 3.9 °C | 39.88 mm |
| April | 1.3 °C | 12.8 °C | 69.85 mm |
| May | 8.3 °C | 20.1 °C | 102.87 mm |
| June | 14.4 °C | 25.7 °C | 128.27 mm |
| July | 16.4 °C | 27.9 °C | 93.73 mm |
| August | 15 °C | 26.5 °C | 99.06 mm |
| September | 10.2 °C | 22.7 °C | 78.99 mm |
| October | 2.9 °C | 14.6 °C | 61.21 mm |
| November | -4.2 °C | 5.2 °C | 37.08 mm |
| December | -11.2 °C | -2.6 °C | 27.43 mm |
| Annual | 1.6 °C | 12.4 °C | 780.28 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4b : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |