Charles City, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 36.8 °F (low) to 56.5 °F (high). Annual precipitation averages 37.8 Inches. 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 | 8.4 °F | 25.2 °F | 1.01 in. |
| February | 12.4 °F | 29.4 °F | 1.13 in. |
| March | 24.3 °F | 42.4 °F | 1.96 in. |
| April | 36.2 °F | 58.1 °F | 3.79 in. |
| May | 48.4 °F | 70.0 °F | 5.09 in. |
| June | 59.0 °F | 79.5 °F | 6.29 in. |
| July | 62.3 °F | 82.5 °F | 4.77 in. |
| August | 59.5 °F | 80.3 °F | 4.24 in. |
| September | 51.0 °F | 74.5 °F | 3.7 in. |
| October | 38.7 °F | 61.2 °F | 2.71 in. |
| November | 26.5 °F | 44.3 °F | 1.75 in. |
| December | 15.3 °F | 30.9 °F | 1.36 in. |
| Annual | 36.8 °F | 56.5 °F | 37.8 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |