Thompsonville, Illinois has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.6 °C (low) to 19 °C (high). Annual precipitation averages 1189 Millimeters. Thompsonville is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.8 °C | 4.7 °C | 86.87 mm |
| February | -3.1 °C | 7.4 °C | 75.44 mm |
| March | 1.6 °C | 13 °C | 106.68 mm |
| April | 7.2 °C | 19.5 °C | 132.84 mm |
| May | 13.1 °C | 24.3 °C | 131.83 mm |
| June | 17.8 °C | 29.1 °C | 116.84 mm |
| July | 19.7 °C | 30.8 °C | 100.08 mm |
| August | 18.4 °C | 30.3 °C | 76.96 mm |
| September | 13.9 °C | 27.2 °C | 80.01 mm |
| October | 7.5 °C | 20.9 °C | 87.38 mm |
| November | 1.9 °C | 13.3 °C | 105.66 mm |
| December | -2.5 °C | 7.1 °C | 88.39 mm |
| Annual | 7.6 °C | 19 °C | 1188.98 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |