Grandfield, Oklahoma has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 10.2 °C (low) to 24.3 °C (high). Annual precipitation averages 753.6 Millimeters. 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 | -1.9 °C | 11.9 °C | 30.23 mm |
| February | -0.2 °C | 14.2 °C | 37.85 mm |
| March | 4.6 °C | 19.1 °C | 57.4 mm |
| April | 8.9 °C | 23.8 °C | 71.12 mm |
| May | 15 °C | 28.8 °C | 104.9 mm |
| June | 20.2 °C | 33.6 °C | 97.28 mm |
| July | 22.2 °C | 36.3 °C | 56.39 mm |
| August | 21.8 °C | 36.1 °C | 59.18 mm |
| September | 17.4 °C | 31.4 °C | 73.15 mm |
| October | 10.7 °C | 25.2 °C | 79.25 mm |
| November | 4.2 °C | 18.1 °C | 48.01 mm |
| December | -0.9 °C | 12.5 °C | 38.86 mm |
| Annual | 10.2 °C | 24.3 °C | 753.62 mm |
| 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 : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 7b : -15°C to -12.2°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |