Arthur, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.2 °C (low) to 17.2 °C (high). Annual precipitation averages 1012.7 Millimeters. Arthur 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 | -7.1 °C | 1.7 °C | 61.21 mm |
| February | -5.4 °C | 4.2 °C | 53.59 mm |
| March | -0.3 °C | 10.6 °C | 72.39 mm |
| April | 5.6 °C | 17.8 °C | 114.05 mm |
| May | 12 °C | 23.6 °C | 114.3 mm |
| June | 16.9 °C | 28.4 °C | 111.51 mm |
| July | 18.6 °C | 29.9 °C | 102.87 mm |
| August | 17.3 °C | 29.2 °C | 68.07 mm |
| September | 13 °C | 26.5 °C | 79.25 mm |
| October | 6.6 °C | 19.4 °C | 85.34 mm |
| November | 0.6 °C | 11.1 °C | 85.6 mm |
| December | -3.8 °C | 4.4 °C | 64.52 mm |
| Annual | 6.2 °C | 17.2 °C | 1012.7 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 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |