Grayson, Kentucky has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 5.6 °C (low) to 19.1 °C (high). Annual precipitation averages 1160.8 Millimeters. Grayson is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.6 °C | 5.7 °C | 80.26 mm |
| February | -4.4 °C | 7.9 °C | 81.28 mm |
| March | -1.1 °C | 13.3 °C | 108.2 mm |
| April | 4.4 °C | 20.2 °C | 105.66 mm |
| May | 10.3 °C | 24.6 °C | 121.41 mm |
| June | 15.1 °C | 28.5 °C | 113.03 mm |
| July | 17.5 °C | 30.3 °C | 129.03 mm |
| August | 16.5 °C | 29.8 °C | 92.71 mm |
| September | 12.3 °C | 26.8 °C | 84.33 mm |
| October | 5.4 °C | 20.8 °C | 74.42 mm |
| November | -0.4 °C | 13.7 °C | 74.68 mm |
| December | -3.2 °C | 7.9 °C | 95.76 mm |
| Annual | 5.6 °C | 19.1 °C | 1160.77 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 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 | Cfa - Humid Subtropical Climate |