Chelsea, Oklahoma has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 8.6 °C (low) to 21.3 °C (high). Annual precipitation averages 1129 Millimeters. Chelsea is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -3.8 °C | 8.3 °C | 51.31 mm |
| February | -2 °C | 10.9 °C | 52.83 mm |
| March | 2.8 °C | 16.1 °C | 88.14 mm |
| April | 7.9 °C | 21.3 °C | 112.52 mm |
| May | 13.7 °C | 25.3 °C | 160.27 mm |
| June | 18.8 °C | 30.1 °C | 131.83 mm |
| July | 21.1 °C | 33.1 °C | 95 mm |
| August | 20.1 °C | 33.1 °C | 84.33 mm |
| September | 15.5 °C | 28.8 °C | 108.71 mm |
| October | 8.8 °C | 22.5 °C | 100.08 mm |
| November | 2.7 °C | 15.9 °C | 81.03 mm |
| December | -2.2 °C | 9.7 °C | 62.99 mm |
| Annual | 8.6 °C | 21.3 °C | 1129.04 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |