Brilliant, Ohio has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.8 °C (low) to 17 °C (high). Annual precipitation averages 1071.1 Millimeters. Brilliant is located in USDA Plant Hardiness Zone 7a. 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 | -5.8 °C | 3.2 °C | 84.84 mm |
| February | -4.9 °C | 4.9 °C | 65.28 mm |
| March | -1.2 °C | 10.2 °C | 84.58 mm |
| April | 4.4 °C | 17.5 °C | 96.01 mm |
| May | 10.1 °C | 22.9 °C | 106.17 mm |
| June | 14.9 °C | 27.2 °C | 111.25 mm |
| July | 17.4 °C | 28.9 °C | 106.43 mm |
| August | 16.6 °C | 28.3 °C | 92.2 mm |
| September | 12.8 °C | 25.1 °C | 89.15 mm |
| October | 6.4 °C | 18.5 °C | 80.52 mm |
| November | 1.1 °C | 11.5 °C | 75.44 mm |
| December | -2.7 °C | 5.6 °C | 79.25 mm |
| Annual | 5.8 °C | 17 °C | 1071.12 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 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |