Winchester, Idaho has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 34.8 °F (low) to 55.6 °F (high). Annual precipitation averages 24.2 Inches. Winchester is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 23.1 °F | 36.4 °F | 2.25 in. |
| February | 23.9 °F | 39.5 °F | 1.52 in. |
| March | 27.4 °F | 45.4 °F | 2.94 in. |
| April | 32.3 °F | 52.3 °F | 3.07 in. |
| May | 38.5 °F | 61.0 °F | 2.87 in. |
| June | 43.9 °F | 67.5 °F | 2.38 in. |
| July | 50.1 °F | 79.1 °F | 0.93 in. |
| August | 50.0 °F | 80.0 °F | 0.8 in. |
| September | 42.9 °F | 70.6 °F | 1.0 in. |
| October | 35.3 °F | 56.7 °F | 1.76 in. |
| November | 27.5 °F | 43.0 °F | 2.42 in. |
| December | 22.2 °F | 35.4 °F | 2.25 in. |
| Annual | 34.8 °F | 55.6 °F | 24.19 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |