Alpha, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40 °F (low) to 60 °F (high). Annual precipitation averages 37.9 Inches. Alpha is located in USDA Plant Hardiness Zone 5b. 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 | 13.9 °F | 30.4 °F | 1.64 in. |
| February | 17.3 °F | 35.0 °F | 1.88 in. |
| March | 27.8 °F | 48.3 °F | 2.32 in. |
| April | 38.6 °F | 61.4 °F | 3.81 in. |
| May | 50.7 °F | 72.2 °F | 4.88 in. |
| June | 60.6 °F | 80.9 °F | 4.83 in. |
| July | 64.0 °F | 83.9 °F | 3.92 in. |
| August | 61.9 °F | 82.3 °F | 3.74 in. |
| September | 53.6 °F | 76.6 °F | 3.64 in. |
| October | 41.9 °F | 64.0 °F | 2.9 in. |
| November | 30.1 °F | 48.6 °F | 2.33 in. |
| December | 19.9 °F | 35.9 °F | 1.99 in. |
| Annual | 40 °F | 60 °F | 37.88 in. |
| 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 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |