Charles City, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.7 °C (low) to 13.6 °C (high). Annual precipitation averages 960.1 Millimeters. Charles City 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 | -13.1 °C | -3.8 °C | 25.65 mm |
| February | -10.9 °C | -1.4 °C | 28.7 mm |
| March | -4.3 °C | 5.8 °C | 49.78 mm |
| April | 2.3 °C | 14.5 °C | 96.27 mm |
| May | 9.1 °C | 21.1 °C | 129.29 mm |
| June | 15 °C | 26.4 °C | 159.77 mm |
| July | 16.8 °C | 28.1 °C | 121.16 mm |
| August | 15.3 °C | 26.8 °C | 107.7 mm |
| September | 10.6 °C | 23.6 °C | 93.98 mm |
| October | 3.7 °C | 16.2 °C | 68.83 mm |
| November | -3.1 °C | 6.8 °C | 44.45 mm |
| December | -9.3 °C | -0.6 °C | 34.54 mm |
| Annual | 2.7 °C | 13.6 °C | 960.12 mm |
| 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 : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |