Riley, Indiana has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 43.5 °F (low) to 63.8 °F (high). Annual precipitation averages 44.8 Inches. Riley is located in USDA Plant Hardiness Zone 6a. 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 | 20.5 °F | 36.5 °F | 3.17 in. |
| February | 23.4 °F | 41.7 °F | 2.54 in. |
| March | 32.5 °F | 52.4 °F | 3.42 in. |
| April | 43.1 °F | 64.5 °F | 4.95 in. |
| May | 53.5 °F | 74.8 °F | 4.72 in. |
| June | 62.3 °F | 83.2 °F | 5.15 in. |
| July | 65.4 °F | 86.1 °F | 4.31 in. |
| August | 63.1 °F | 84.9 °F | 2.84 in. |
| September | 55.3 °F | 79.5 °F | 3.25 in. |
| October | 44.0 °F | 67.3 °F | 3.74 in. |
| November | 33.7 °F | 53.1 °F | 3.69 in. |
| December | 25.4 °F | 41.1 °F | 3.03 in. |
| Annual | 43.5 °F | 63.8 °F | 44.81 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |