Mason City, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.2 °C (low) to 13.1 °C (high). Annual precipitation averages 922.3 Millimeters. Mason 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 | -13.8 °C | -4.4 °C | 23.62 mm |
| February | -11.6 °C | -1.9 °C | 28.7 mm |
| March | -4.8 °C | 5.1 °C | 51.31 mm |
| April | 1.7 °C | 13.6 °C | 101.35 mm |
| May | 8.6 °C | 20.4 °C | 135.89 mm |
| June | 14.6 °C | 26.1 °C | 138.94 mm |
| July | 16.5 °C | 27.7 °C | 116.84 mm |
| August | 14.9 °C | 26.4 °C | 97.28 mm |
| September | 10.2 °C | 23.1 °C | 84.84 mm |
| October | 3.2 °C | 15.6 °C | 65.53 mm |
| November | -3.7 °C | 6.4 °C | 44.7 mm |
| December | -9.8 °C | -1.2 °C | 33.27 mm |
| Annual | 2.2 °C | 13.1 °C | 922.27 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 | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |