Arrowsmith, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.8 °C (low) to 15.9 °C (high). Annual precipitation averages 963.2 Millimeters. Arrowsmith is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.8 °C | 0.1 °C | 56.9 mm |
| February | -7.3 °C | 2.6 °C | 48.01 mm |
| March | -2.1 °C | 9.2 °C | 65.53 mm |
| April | 4 °C | 16.4 °C | 91.95 mm |
| May | 10.8 °C | 22.6 °C | 112.27 mm |
| June | 16.3 °C | 27.3 °C | 109.98 mm |
| July | 17.6 °C | 28.8 °C | 101.35 mm |
| August | 16.3 °C | 28.1 °C | 86.87 mm |
| September | 12.1 °C | 25.2 °C | 85.6 mm |
| October | 5.7 °C | 18.2 °C | 83.82 mm |
| November | -0.7 °C | 9.9 °C | 66.8 mm |
| December | -6 °C | 2.8 °C | 54.1 mm |
| Annual | 4.8 °C | 15.9 °C | 963.18 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 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 |