Spring Bay, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.3 °C (low) to 16.8 °C (high). Annual precipitation averages 972.8 Millimeters. Spring Bay 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 | -8.5 °C | 0.6 °C | 53.09 mm |
| February | -6.7 °C | 3.1 °C | 50.29 mm |
| March | -1.2 °C | 9.9 °C | 64.77 mm |
| April | 4.6 °C | 17.4 °C | 96.77 mm |
| May | 10.7 °C | 23.3 °C | 121.92 mm |
| June | 16.1 °C | 28.3 °C | 111.76 mm |
| July | 18.2 °C | 30.1 °C | 95.76 mm |
| August | 17.2 °C | 29.2 °C | 90.42 mm |
| September | 12.6 °C | 26 °C | 89.41 mm |
| October | 5.8 °C | 19.1 °C | 77.72 mm |
| November | -0.1 °C | 10.6 °C | 67.82 mm |
| December | -5.3 °C | 3.4 °C | 53.09 mm |
| Annual | 5.3 °C | 16.8 °C | 972.82 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 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |