Pentwater, Michigan has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.1 °C (low) to 12.5 °C (high). Annual precipitation averages 907.5 Millimeters. Pentwater is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.3 °C | -1.2 °C | 61.47 mm |
| February | -7.1 °C | -0.2 °C | 45.97 mm |
| March | -3.9 °C | 4.4 °C | 53.59 mm |
| April | 1.7 °C | 11.4 °C | 85.6 mm |
| May | 7.2 °C | 17.9 °C | 92.71 mm |
| June | 12.6 °C | 23.2 °C | 86.61 mm |
| July | 15.8 °C | 25.2 °C | 82.3 mm |
| August | 15.7 °C | 24.7 °C | 85.6 mm |
| September | 11.9 °C | 21.3 °C | 78.49 mm |
| October | 5.7 °C | 14.3 °C | 97.28 mm |
| November | 0.7 °C | 7.3 °C | 76.45 mm |
| December | -4.1 °C | 1.6 °C | 61.47 mm |
| Annual | 4.1 °C | 12.5 °C | 907.54 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |