Miller, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.1 °C (low) to 13.1 °C (high). Annual precipitation averages 874.3 Millimeters. Miller is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -13.9 °C | -4.6 °C | 23.62 mm |
| February | -11.6 °C | -1.9 °C | 24.38 mm |
| March | -4.7 °C | 5.1 °C | 50.04 mm |
| April | 1.7 °C | 13.6 °C | 95 mm |
| May | 8.6 °C | 20.5 °C | 123.44 mm |
| June | 14.6 °C | 26 °C | 135.64 mm |
| July | 16.4 °C | 27.7 °C | 110.74 mm |
| August | 14.8 °C | 26.4 °C | 98.04 mm |
| September | 9.9 °C | 23.1 °C | 81.28 mm |
| October | 3.1 °C | 15.7 °C | 59.18 mm |
| November | -3.7 °C | 6.3 °C | 40.13 mm |
| December | -10.1 °C | -1.3 °C | 32.77 mm |
| Annual | 2.1 °C | 13.1 °C | 874.26 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| 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 |