Robertsville, Ohio has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.9 °C (low) to 15.6 °C (high). Annual precipitation averages 1046 Millimeters. Robertsville is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7 °C | 1.3 °C | 77.72 mm |
| February | -6.4 °C | 2.9 °C | 57.66 mm |
| March | -2.1 °C | 8.3 °C | 82.3 mm |
| April | 3.8 °C | 15.8 °C | 91.95 mm |
| May | 9.4 °C | 21.4 °C | 103.38 mm |
| June | 14.7 °C | 26.2 °C | 114.05 mm |
| July | 16.7 °C | 28.3 °C | 111.76 mm |
| August | 15.7 °C | 27.3 °C | 92.46 mm |
| September | 11.9 °C | 23.9 °C | 86.87 mm |
| October | 5.8 °C | 17.4 °C | 79.76 mm |
| November | 0.6 °C | 10.1 °C | 73.91 mm |
| December | -3.8 °C | 4.1 °C | 74.17 mm |
| Annual | 4.9 °C | 15.6 °C | 1045.99 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| 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 |