Bertha, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.7 °C (low) to 10.5 °C (high). Annual precipitation averages 688.3 Millimeters. Bertha is located in USDA Plant Hardiness Zone 4a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -18.2 °C | -7.6 °C | 14.99 mm |
| February | -16.2 °C | -4.7 °C | 15.24 mm |
| March | -8.9 °C | 2.3 °C | 27.94 mm |
| April | -1.1 °C | 11 °C | 53.34 mm |
| May | 6.3 °C | 18.4 °C | 88.14 mm |
| June | 12.3 °C | 23.4 °C | 113.28 mm |
| July | 14.7 °C | 26.1 °C | 108.2 mm |
| August | 13.2 °C | 25.2 °C | 83.57 mm |
| September | 8.5 °C | 20.6 °C | 69.34 mm |
| October | 1.2 °C | 12.2 °C | 70.87 mm |
| November | -6.1 °C | 3.1 °C | 24.38 mm |
| December | -13.6 °C | -4.6 °C | 19.05 mm |
| Annual | -0.7 °C | 10.5 °C | 688.34 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |