Melvin, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.9 °C (low) to 16.2 °C (high). Annual precipitation averages 969 Millimeters. Melvin 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 | -8.6 °C | 0.2 °C | 54.86 mm |
| February | -6.9 °C | 2.8 °C | 46.74 mm |
| March | -1.7 °C | 9.3 °C | 66.04 mm |
| April | 4.2 °C | 16.8 °C | 96.01 mm |
| May | 10.8 °C | 22.9 °C | 113.28 mm |
| June | 16 °C | 27.7 °C | 112.01 mm |
| July | 17.6 °C | 29.1 °C | 104.39 mm |
| August | 16.3 °C | 28.3 °C | 91.19 mm |
| September | 11.9 °C | 25.9 °C | 77.47 mm |
| October | 5.5 °C | 18.7 °C | 83.31 mm |
| November | -0.3 °C | 10.1 °C | 69.34 mm |
| December | -5.7 °C | 2.9 °C | 54.36 mm |
| Annual | 4.9 °C | 16.2 °C | 969 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 |