Garrison, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 12.5 °C (low) to 25.2 °C (high). Annual precipitation averages 1316.7 Millimeters. Garrison is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 11 - Mar. 20 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.2 °C | 14.7 °C | 119.38 mm |
| February | 4.2 °C | 17.1 °C | 104.9 mm |
| March | 7.9 °C | 21.1 °C | 118.87 mm |
| April | 11.7 °C | 25.1 °C | 118.36 mm |
| May | 17 °C | 29 °C | 112.78 mm |
| June | 20.9 °C | 32.5 °C | 120.14 mm |
| July | 22.4 °C | 34.3 °C | 78.23 mm |
| August | 22.1 °C | 34.8 °C | 88.39 mm |
| September | 18.6 °C | 31.6 °C | 96.77 mm |
| October | 12.4 °C | 26.3 °C | 114.81 mm |
| November | 6.9 °C | 20 °C | 114.3 mm |
| December | 3.2 °C | 15.6 °C | 129.79 mm |
| Annual | 12.5 °C | 25.2 °C | 1316.72 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| Average Days With Frost | 30-40 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |