Thomasboro, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.3 °C (low) to 16.7 °C (high). Annual precipitation averages 1012.7 Millimeters. Thomasboro is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.2 °C | 0.7 °C | 57.91 mm |
| February | -6.4 °C | 3.3 °C | 51.82 mm |
| March | -1.3 °C | 9.7 °C | 69.85 mm |
| April | 4.5 °C | 17.3 °C | 102.87 mm |
| May | 11.2 °C | 23.5 °C | 112.78 mm |
| June | 16.3 °C | 28.2 °C | 118.62 mm |
| July | 17.8 °C | 29.6 °C | 107.7 mm |
| August | 16.5 °C | 28.8 °C | 86.11 mm |
| September | 12.4 °C | 26.2 °C | 81.03 mm |
| October | 5.8 °C | 19 °C | 85.34 mm |
| November | -0.1 °C | 10.5 °C | 78.49 mm |
| December | -5.1 °C | 3.4 °C | 60.2 mm |
| Annual | 5.3 °C | 16.7 °C | 1012.72 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |