Troy, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 8.5 °C (low) to 18.9 °C (high). Annual precipitation averages 1132.6 Millimeters. Troy is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.6 °C | 4.3 °C | 69.6 mm |
| February | -2.9 °C | 7.3 °C | 61.47 mm |
| March | 2.1 °C | 13.1 °C | 88.14 mm |
| April | 8 °C | 19.5 °C | 126.24 mm |
| May | 14.1 °C | 24.6 °C | 132.08 mm |
| June | 19 °C | 29.4 °C | 121.92 mm |
| July | 21.1 °C | 31.1 °C | 107.95 mm |
| August | 19.9 °C | 30.6 °C | 95 mm |
| September | 15.3 °C | 27.1 °C | 82.8 mm |
| October | 9.1 °C | 20.6 °C | 83.57 mm |
| November | 2.6 °C | 12.7 °C | 93.47 mm |
| December | -2.1 °C | 6.8 °C | 70.36 mm |
| Annual | 8.5 °C | 18.9 °C | 1132.6 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |