Glenn Heights, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 12.8 °C (low) to 24.7 °C (high). Annual precipitation averages 1032.2 Millimeters. Glenn Heights is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 1 - Mar. 10 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.9 °C | 13.7 °C | 70.87 mm |
| February | 3.8 °C | 15.8 °C | 73.91 mm |
| March | 7.8 °C | 19.9 °C | 92.96 mm |
| April | 11.9 °C | 24.2 °C | 95.25 mm |
| May | 17.2 °C | 28.2 °C | 113.28 mm |
| June | 21.6 °C | 32.7 °C | 97.79 mm |
| July | 23.3 °C | 35 °C | 54.61 mm |
| August | 23.2 °C | 35.3 °C | 65.79 mm |
| September | 19.2 °C | 31.7 °C | 83.31 mm |
| October | 13 °C | 25.8 °C | 123.44 mm |
| November | 7.4 °C | 19.4 °C | 76.45 mm |
| December | 2.8 °C | 14.5 °C | 84.58 mm |
| Annual | 12.8 °C | 24.7 °C | 1032.24 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 1 - Mar. 10 |
| Average Days With Frost | 30-40 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |