Shamrock, Oklahoma has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.6 °C (low) to 22 °C (high). Annual precipitation averages 1003.3 Millimeters. Shamrock 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 Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -2.7 °C | 9.6 °C | 38.35 mm |
| February | -1.1 °C | 11.7 °C | 44.45 mm |
| March | 3.8 °C | 16.9 °C | 74.42 mm |
| April | 8.8 °C | 22.1 °C | 104.65 mm |
| May | 14.6 °C | 26.1 °C | 141.99 mm |
| June | 19.7 °C | 30.8 °C | 122.94 mm |
| July | 21.9 °C | 33.8 °C | 90.93 mm |
| August | 21.3 °C | 33.7 °C | 85.6 mm |
| September | 16.7 °C | 29.3 °C | 93.22 mm |
| October | 10 °C | 23.2 °C | 95 mm |
| November | 3.6 °C | 16.4 °C | 62.23 mm |
| December | -1.3 °C | 10.2 °C | 49.53 mm |
| Annual | 9.6 °C | 22 °C | 1003.31 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 7b : -15°C to -12.2°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |