Harrison, Idaho has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 2.6 °C (low) to 14.9 °C (high). Annual precipitation averages 610.9 Millimeters. Harrison is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4 °C | 2.4 °C | 77.72 mm |
| February | -3.8 °C | 5 °C | 54.1 mm |
| March | -1.4 °C | 9.6 °C | 61.47 mm |
| April | 1.4 °C | 14.2 °C | 47.5 mm |
| May | 5.4 °C | 19.5 °C | 52.83 mm |
| June | 8.7 °C | 22.8 °C | 41.66 mm |
| July | 11.1 °C | 28.8 °C | 15.24 mm |
| August | 10.6 °C | 29.1 °C | 17.53 mm |
| September | 6.4 °C | 23.7 °C | 22.61 mm |
| October | 1.9 °C | 15.2 °C | 50.55 mm |
| November | -1.3 °C | 6.9 °C | 79.5 mm |
| December | -4.1 °C | 2 °C | 90.17 mm |
| Annual | 2.6 °C | 14.9 °C | 610.88 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 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 | Severe Drought |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |