Forest Hill, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 13.2 °C (low) to 25 °C (high). Annual precipitation averages 969.5 Millimeters. Forest Hill 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 | 13.8 °C | 64.01 mm |
| February | 3.9 °C | 16.1 °C | 67.56 mm |
| March | 8.2 °C | 20.2 °C | 88.9 mm |
| April | 12.3 °C | 24.6 °C | 84.07 mm |
| May | 17.7 °C | 28.7 °C | 115.57 mm |
| June | 22.1 °C | 33.2 °C | 97.03 mm |
| July | 23.9 °C | 35.6 °C | 52.58 mm |
| August | 23.8 °C | 35.7 °C | 62.48 mm |
| September | 19.7 °C | 31.8 °C | 81.79 mm |
| October | 13.6 °C | 26.1 °C | 111.25 mm |
| November | 7.8 °C | 19.5 °C | 72.9 mm |
| December | 3.1 °C | 14.8 °C | 71.37 mm |
| Annual | 13.2 °C | 25 °C | 969.51 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 |