Massac, Kentucky has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 8.9 °C (low) to 20.3 °C (high). Annual precipitation averages 1292.9 Millimeters. Massac is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -2.5 °C | 7 °C | 102.36 mm |
| February | -1 °C | 9.7 °C | 95 mm |
| March | 3.3 °C | 14.9 °C | 122.17 mm |
| April | 8.4 °C | 20.8 °C | 132.08 mm |
| May | 14 °C | 25.6 °C | 133.86 mm |
| June | 18.7 °C | 29.8 °C | 116.33 mm |
| July | 20.6 °C | 31.4 °C | 105.41 mm |
| August | 19.3 °C | 31.2 °C | 76.2 mm |
| September | 15.1 °C | 28 °C | 89.66 mm |
| October | 8.7 °C | 21.8 °C | 97.79 mm |
| November | 3 °C | 14.5 °C | 107.19 mm |
| December | -0.8 °C | 8.8 °C | 114.81 mm |
| Annual | 8.9 °C | 20.3 °C | 1292.86 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |