Grandfield, Oklahoma has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 50.3 °F (low) to 75.7 °F (high). Annual precipitation averages 29.7 Inches. Grandfield is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 28.6 °F | 53.5 °F | 1.19 in. |
| February | 31.7 °F | 57.6 °F | 1.49 in. |
| March | 40.2 °F | 66.4 °F | 2.26 in. |
| April | 48.0 °F | 74.9 °F | 2.8 in. |
| May | 59.0 °F | 83.8 °F | 4.13 in. |
| June | 68.3 °F | 92.5 °F | 3.83 in. |
| July | 72.0 °F | 97.3 °F | 2.22 in. |
| August | 71.2 °F | 96.9 °F | 2.33 in. |
| September | 63.3 °F | 88.6 °F | 2.88 in. |
| October | 51.2 °F | 77.3 °F | 3.12 in. |
| November | 39.5 °F | 64.5 °F | 1.89 in. |
| December | 30.4 °F | 54.5 °F | 1.53 in. |
| Annual | 50.3 °F | 75.7 °F | 29.67 in. |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8a : 10°F to 15°F |
| Plant Hardiness Zone - 2012 | Zone 7b : 5°F to 10°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |