Seymour, Indiana has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.5 °C (low) to 18 °C (high). Annual precipitation averages 1249.7 Millimeters. Seymour is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.3 °C | 3.9 °C | 91.69 mm |
| February | -4.1 °C | 6.4 °C | 74.42 mm |
| March | 0.3 °C | 12.1 °C | 104.65 mm |
| April | 5.8 °C | 18.7 °C | 133.86 mm |
| May | 11.7 °C | 23.7 °C | 135.89 mm |
| June | 16.3 °C | 27.9 °C | 131.57 mm |
| July | 18.3 °C | 29.6 °C | 107.7 mm |
| August | 17.2 °C | 29.3 °C | 103.12 mm |
| September | 12.9 °C | 26.2 °C | 83.82 mm |
| October | 6.3 °C | 19.7 °C | 91.69 mm |
| November | 1.1 °C | 12.4 °C | 95.5 mm |
| December | -3 °C | 6.2 °C | 95.76 mm |
| Annual | 6.5 °C | 18 °C | 1249.67 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |