Sulphur, Oklahoma has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.9 °C (low) to 22.9 °C (high). Annual precipitation averages 1014.7 Millimeters. Sulphur 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 | -2.2 °C | 11.1 °C | 49.28 mm |
| February | -0.2 °C | 13.3 °C | 52.32 mm |
| March | 4.7 °C | 18.2 °C | 79.76 mm |
| April | 9.1 °C | 22.8 °C | 89.92 mm |
| May | 14.6 °C | 26.4 °C | 136.14 mm |
| June | 19.7 °C | 31.1 °C | 116.59 mm |
| July | 21.7 °C | 34.1 °C | 89.66 mm |
| August | 21.1 °C | 34.4 °C | 70.1 mm |
| September | 16.8 °C | 30.1 °C | 104.39 mm |
| October | 10.2 °C | 24.1 °C | 100.58 mm |
| November | 4.1 °C | 17.6 °C | 61.98 mm |
| December | -0.9 °C | 11.9 °C | 64.01 mm |
| Annual | 9.9 °C | 22.9 °C | 1014.73 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 7b : -15°C to -12.2°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |