Grayson, Oklahoma has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.5 °C (low) to 22.3 °C (high). Annual precipitation averages 1112.8 Millimeters. Grayson is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -2.7 °C | 9.9 °C | 53.34 mm |
| February | -0.7 °C | 12.2 °C | 54.61 mm |
| March | 4.2 °C | 17.3 °C | 84.58 mm |
| April | 8.8 °C | 22.1 °C | 113.79 mm |
| May | 14.4 °C | 26.1 °C | 145.29 mm |
| June | 19.6 °C | 30.8 °C | 119.38 mm |
| July | 21.4 °C | 33.7 °C | 103.38 mm |
| August | 20.8 °C | 33.8 °C | 79.25 mm |
| September | 16.2 °C | 29.7 °C | 111.51 mm |
| October | 9.6 °C | 23.5 °C | 101.6 mm |
| November | 3.8 °C | 17.1 °C | 80.52 mm |
| December | -1.1 °C | 11.1 °C | 65.53 mm |
| Annual | 9.5 °C | 22.3 °C | 1112.78 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 7b : -15°C to -12.2°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |