Fernwood, Idaho has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 1.7 °C (low) to 14.3 °C (high). Annual precipitation averages 880.9 Millimeters. Fernwood is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.1 °C | 2.2 °C | 119.89 mm |
| February | -3.9 °C | 4.2 °C | 89.66 mm |
| March | -1.9 °C | 8.6 °C | 96.01 mm |
| April | 0.9 °C | 13.1 °C | 67.31 mm |
| May | 4.3 °C | 19.1 °C | 77.47 mm |
| June | 7.2 °C | 22.3 °C | 57.91 mm |
| July | 9.1 °C | 28.3 °C | 20.57 mm |
| August | 8.7 °C | 28.8 °C | 20.57 mm |
| September | 5.2 °C | 23.2 °C | 23.62 mm |
| October | 1.4 °C | 14.3 °C | 73.91 mm |
| November | -1.6 °C | 5.9 °C | 107.7 mm |
| December | -4.7 °C | 1.3 °C | 126.24 mm |
| Annual | 1.7 °C | 14.3 °C | 880.86 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 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 | Severe Drought |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |