Shamrock, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.8 °C (low) to 22.8 °C (high). Annual precipitation averages 633.5 Millimeters. Shamrock 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 Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.1 °C | 10.8 °C | 20.07 mm |
| February | -2.4 °C | 12.9 °C | 24.89 mm |
| March | 2.1 °C | 18.1 °C | 41.15 mm |
| April | 6.6 °C | 22.7 °C | 60.71 mm |
| May | 12.4 °C | 27.2 °C | 90.42 mm |
| June | 17.8 °C | 31.8 °C | 86.61 mm |
| July | 20.2 °C | 34.5 °C | 64.26 mm |
| August | 19.4 °C | 33.9 °C | 68.83 mm |
| September | 15.1 °C | 29.5 °C | 66.04 mm |
| October | 8.2 °C | 23.6 °C | 51.56 mm |
| November | 1.6 °C | 16.8 °C | 32.77 mm |
| December | -3.1 °C | 11.3 °C | 26.16 mm |
| Annual | 7.8 °C | 22.8 °C | 633.47 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| 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 | Severe Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |