Harrison, Idaho has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 36.6 °F (low) to 58.9 °F (high). Annual precipitation averages 24.1 Inches. 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 | 24.8 °F | 36.4 °F | 3.06 in. |
| February | 25.1 °F | 41.0 °F | 2.13 in. |
| March | 29.4 °F | 49.3 °F | 2.42 in. |
| April | 34.5 °F | 57.5 °F | 1.87 in. |
| May | 41.7 °F | 67.1 °F | 2.08 in. |
| June | 47.6 °F | 73.1 °F | 1.64 in. |
| July | 52.0 °F | 83.9 °F | 0.6 in. |
| August | 51.0 °F | 84.4 °F | 0.69 in. |
| September | 43.5 °F | 74.6 °F | 0.89 in. |
| October | 35.5 °F | 59.4 °F | 1.99 in. |
| November | 29.6 °F | 44.4 °F | 3.13 in. |
| December | 24.6 °F | 35.6 °F | 3.55 in. |
| Annual | 36.6 °F | 58.9 °F | 24.05 in. |
| 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 : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |