Rittman, Ohio has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 5 °C (low) to 15.4 °C (high). Annual precipitation averages 1011.9 Millimeters. Rittman 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.2 °C | 1.1 °C | 70.1 mm |
| February | -6.5 °C | 2.6 °C | 52.58 mm |
| March | -2.1 °C | 8 °C | 75.18 mm |
| April | 3.8 °C | 15.4 °C | 93.22 mm |
| May | 9.8 °C | 21.3 °C | 102.62 mm |
| June | 14.9 °C | 26.1 °C | 108.2 mm |
| July | 16.9 °C | 28.1 °C | 102.11 mm |
| August | 15.9 °C | 27.3 °C | 95.25 mm |
| September | 11.9 °C | 23.9 °C | 88.39 mm |
| October | 5.9 °C | 17.1 °C | 81.53 mm |
| November | 0.6 °C | 9.9 °C | 72.39 mm |
| December | -3.8 °C | 3.7 °C | 70.36 mm |
| Annual | 5 °C | 15.4 °C | 1011.93 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°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 |