Bruneau, Idaho has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 4.2 °C (low) to 19.2 °C (high). Annual precipitation averages 190.5 Millimeters. Bruneau 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -3.9 °C | 4.9 °C | 23.62 mm |
| February | -2.6 °C | 8.9 °C | 13.46 mm |
| March | 0.5 °C | 14.2 °C | 20.07 mm |
| April | 3.1 °C | 18.4 °C | 20.32 mm |
| May | 7.4 °C | 23.5 °C | 27.69 mm |
| June | 11.2 °C | 28.5 °C | 16.26 mm |
| July | 15.1 °C | 34.5 °C | 2.54 mm |
| August | 13.8 °C | 33.7 °C | 2.54 mm |
| September | 8.8 °C | 28 °C | 7.11 mm |
| October | 3.2 °C | 20.1 °C | 15.75 mm |
| November | -1.5 °C | 10.9 °C | 18.8 mm |
| December | -4.3 °C | 4.8 °C | 22.35 mm |
| Annual | 4.2 °C | 19.2 °C | 190.51 mm |
| 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 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |