Gilmer, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 12.2 °C (low) to 24.5 °C (high). Annual precipitation averages 1210 Millimeters. Gilmer 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 | 1.7 °C | 13.7 °C | 96.77 mm |
| February | 3.5 °C | 16 °C | 102.36 mm |
| March | 7.3 °C | 20.3 °C | 115.57 mm |
| April | 11.3 °C | 24.4 °C | 108.2 mm |
| May | 16.7 °C | 28.2 °C | 118.11 mm |
| June | 20.9 °C | 32.1 °C | 101.85 mm |
| July | 22.6 °C | 34.1 °C | 73.41 mm |
| August | 22.1 °C | 34.4 °C | 70.36 mm |
| September | 18.4 °C | 31.2 °C | 92.2 mm |
| October | 12.1 °C | 25.6 °C | 115.82 mm |
| November | 6.7 °C | 19.3 °C | 98.3 mm |
| December | 2.7 °C | 14.7 °C | 117.09 mm |
| Annual | 12.2 °C | 24.5 °C | 1210.04 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 | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |