Okmulgee, Oklahoma has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.2 °C (low) to 22.3 °C (high). Annual precipitation averages 1096.5 Millimeters. Okmulgee is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -2.9 °C | 9.9 °C | 49.28 mm |
| February | -1.1 °C | 12.2 °C | 53.59 mm |
| March | 3.9 °C | 17.2 °C | 81.28 mm |
| April | 8.5 °C | 22.1 °C | 112.52 mm |
| May | 14.2 °C | 26.1 °C | 147.57 mm |
| June | 19.4 °C | 30.8 °C | 118.87 mm |
| July | 21.2 °C | 33.8 °C | 107.7 mm |
| August | 20.5 °C | 33.8 °C | 81.79 mm |
| September | 15.8 °C | 29.7 °C | 99.31 mm |
| October | 9.2 °C | 23.6 °C | 101.09 mm |
| November | 3.4 °C | 17 °C | 79.25 mm |
| December | -1.4 °C | 11 °C | 64.26 mm |
| Annual | 9.2 °C | 22.3 °C | 1096.51 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| 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 | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |