Marietta, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1 °C (low) to 12.5 °C (high). Annual precipitation averages 649 Millimeters. Marietta 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 | -15.6 °C | -5.3 °C | 18.54 mm |
| February | -13.7 °C | -2.9 °C | 18.54 mm |
| March | -6.7 °C | 3.8 °C | 32.51 mm |
| April | 0.5 °C | 12.8 °C | 63.25 mm |
| May | 7.8 °C | 20.3 °C | 76.45 mm |
| June | 14 °C | 25.8 °C | 98.81 mm |
| July | 16.1 °C | 28.1 °C | 93.47 mm |
| August | 14.5 °C | 26.9 °C | 77.72 mm |
| September | 9.6 °C | 22.9 °C | 64.26 mm |
| October | 2.3 °C | 14.8 °C | 56.13 mm |
| November | -4.9 °C | 5.6 °C | 28.19 mm |
| December | -11.8 °C | -2.3 °C | 21.08 mm |
| Annual | 1 °C | 12.5 °C | 648.95 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 | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |