Bertha, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 30.8 °F (low) to 50.8 °F (high). Annual precipitation averages 27.1 Inches. 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 | -0.7 °F | 18.3 °F | 0.59 in. |
| February | 2.8 °F | 23.6 °F | 0.6 in. |
| March | 16.0 °F | 36.2 °F | 1.1 in. |
| April | 30.1 °F | 51.8 °F | 2.1 in. |
| May | 43.3 °F | 65.1 °F | 3.47 in. |
| June | 54.1 °F | 74.1 °F | 4.46 in. |
| July | 58.5 °F | 79.0 °F | 4.26 in. |
| August | 55.7 °F | 77.3 °F | 3.29 in. |
| September | 47.3 °F | 69.0 °F | 2.73 in. |
| October | 34.2 °F | 54.0 °F | 2.79 in. |
| November | 21.0 °F | 37.5 °F | 0.96 in. |
| December | 7.6 °F | 23.8 °F | 0.75 in. |
| Annual | 30.8 °F | 50.8 °F | 27.1 in. |
| 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 : -30°F to -25°F |
| Plant Hardiness Zone - 2012 | Zone 4a : -30°F to -25°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |