Alden, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.3 °C (low) to 14 °C (high). Annual precipitation averages 969.3 Millimeters. Alden is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.5 °C | -1.9 °C | 44.2 mm |
| February | -9.1 °C | 0.3 °C | 45.72 mm |
| March | -3.7 °C | 7 °C | 57.15 mm |
| April | 1.9 °C | 14.1 °C | 95.76 mm |
| May | 8.9 °C | 20.4 °C | 114.3 mm |
| June | 13.9 °C | 25.6 °C | 132.33 mm |
| July | 16.3 °C | 27.7 °C | 97.28 mm |
| August | 15.3 °C | 26.8 °C | 101.85 mm |
| September | 11 °C | 23.3 °C | 92.46 mm |
| October | 4.6 °C | 16.1 °C | 75.44 mm |
| November | -1.4 °C | 8 °C | 61.21 mm |
| December | -7.3 °C | 0.9 °C | 51.56 mm |
| Annual | 3.3 °C | 14 °C | 969.26 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°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 |