Boise, Idaho has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 4.1 °C (low) to 18.3 °C (high). Annual precipitation averages 344.4 Millimeters. Boise is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.2 °C | 4.2 °C | 42.67 mm |
| February | -2.6 °C | 8.2 °C | 30.99 mm |
| March | 0.4 °C | 13.4 °C | 41.4 mm |
| April | 2.8 °C | 17.3 °C | 36.07 mm |
| May | 6.9 °C | 22.6 °C | 41.4 mm |
| June | 10.7 °C | 27.6 °C | 22.86 mm |
| July | 14.5 °C | 33.6 °C | 8.64 mm |
| August | 13.6 °C | 32.7 °C | 5.33 mm |
| September | 9.2 °C | 26.9 °C | 11.68 mm |
| October | 3.6 °C | 19 °C | 22.61 mm |
| November | -1.1 °C | 10.1 °C | 33.27 mm |
| December | -4.2 °C | 4.3 °C | 47.5 mm |
| Annual | 4.1 °C | 18.3 °C | 344.42 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |