Newton, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.1 °C (low) to 15.2 °C (high). Annual precipitation averages 913.1 Millimeters. Newton is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.1 °C | -1.6 °C | 23.88 mm |
| February | -8.9 °C | 1.1 °C | 30.23 mm |
| March | -2.8 °C | 8.3 °C | 51.05 mm |
| April | 3.4 °C | 15.9 °C | 94.49 mm |
| May | 10.3 °C | 21.9 °C | 124.21 mm |
| June | 16.1 °C | 27.2 °C | 130.3 mm |
| July | 18 °C | 29.1 °C | 106.68 mm |
| August | 16.6 °C | 28 °C | 109.98 mm |
| September | 11.7 °C | 24.7 °C | 91.44 mm |
| October | 4.9 °C | 17.3 °C | 67.06 mm |
| November | -1.9 °C | 8.7 °C | 50.55 mm |
| December | -7.7 °C | 1.5 °C | 33.27 mm |
| Annual | 4.1 °C | 15.2 °C | 913.14 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |