Waterloo, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 37.6 °F (low) to 57.6 °F (high). Annual precipitation averages 38.4 Inches. Waterloo is located in USDA Plant Hardiness Zone 5a. 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 | 9.5 °F | 26.5 °F | 1.12 in. |
| February | 13.6 °F | 30.9 °F | 1.21 in. |
| March | 25.1 °F | 44.3 °F | 2.09 in. |
| April | 36.8 °F | 58.8 °F | 4.1 in. |
| May | 49.2 °F | 70.5 °F | 4.85 in. |
| June | 60.0 °F | 80.3 °F | 5.72 in. |
| July | 63.0 °F | 83.3 °F | 4.81 in. |
| August | 60.3 °F | 81.4 °F | 4.24 in. |
| September | 51.5 °F | 75.4 °F | 3.64 in. |
| October | 39.2 °F | 61.9 °F | 2.99 in. |
| November | 26.9 °F | 45.7 °F | 2.02 in. |
| December | 16.3 °F | 32.5 °F | 1.57 in. |
| Annual | 37.6 °F | 57.6 °F | 38.36 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |