Winchester, Idaho has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 1.5 °C (low) to 13.1 °C (high). Annual precipitation averages 614.4 Millimeters. 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 | -4.9 °C | 2.4 °C | 57.15 mm |
| February | -4.5 °C | 4.2 °C | 38.61 mm |
| March | -2.6 °C | 7.4 °C | 74.68 mm |
| April | 0.2 °C | 11.3 °C | 77.98 mm |
| May | 3.6 °C | 16.1 °C | 72.9 mm |
| June | 6.6 °C | 19.7 °C | 60.45 mm |
| July | 10.1 °C | 26.2 °C | 23.62 mm |
| August | 10 °C | 26.7 °C | 20.32 mm |
| September | 6.1 °C | 21.4 °C | 25.4 mm |
| October | 1.8 °C | 13.7 °C | 44.7 mm |
| November | -2.5 °C | 6.1 °C | 61.47 mm |
| December | -5.4 °C | 1.9 °C | 57.15 mm |
| Annual | 1.5 °C | 13.1 °C | 614.43 mm |
| 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 : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |