Waterloo, Indiana has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.3 °C (low) to 15.5 °C (high). Annual precipitation averages 977.7 Millimeters. Waterloo is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.3 °C | 0.1 °C | 60.71 mm |
| February | -7.3 °C | 2.2 °C | 53.34 mm |
| March | -2.7 °C | 8.2 °C | 63.25 mm |
| April | 2.9 °C | 15.8 °C | 92.71 mm |
| May | 9.3 °C | 22.1 °C | 111.51 mm |
| June | 14.8 °C | 27 °C | 100.58 mm |
| July | 16.6 °C | 28.9 °C | 96.52 mm |
| August | 15.4 °C | 27.8 °C | 101.85 mm |
| September | 11.3 °C | 24.6 °C | 83.82 mm |
| October | 5.3 °C | 17.6 °C | 74.93 mm |
| November | -0.3 °C | 9.4 °C | 76.2 mm |
| December | -5.1 °C | 2.8 °C | 62.23 mm |
| Annual | 4.3 °C | 15.5 °C | 977.65 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |