Ionia, Michigan has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.7 °C (low) to 14.1 °C (high). Annual precipitation averages 931.2 Millimeters. Ionia is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.6 °C | -1.1 °C | 60.45 mm |
| February | -8.2 °C | 0.6 °C | 54.1 mm |
| March | -3.9 °C | 6.4 °C | 58.17 mm |
| April | 1.8 °C | 13.9 °C | 93.98 mm |
| May | 8.3 °C | 20.5 °C | 105.41 mm |
| June | 13.9 °C | 25.8 °C | 90.42 mm |
| July | 16 °C | 27.9 °C | 86.11 mm |
| August | 15.1 °C | 26.8 °C | 91.95 mm |
| September | 10.5 °C | 22.8 °C | 77.47 mm |
| October | 4.7 °C | 15.8 °C | 84.33 mm |
| November | -0.4 °C | 8.2 °C | 72.9 mm |
| December | -5 °C | 1.8 °C | 55.88 mm |
| Annual | 3.7 °C | 14.1 °C | 931.17 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |