Lost River, Idaho has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -3.2 °C (low) to 12.2 °C (high). Annual precipitation averages 324.4 Millimeters. Lost River is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Jun. 1 - Jun. 10 through the first frost around Aug. 21 - Aug. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -14.6 °C | -1.9 °C | 31.75 mm |
| February | -12.9 °C | 0.6 °C | 25.15 mm |
| March | -7.9 °C | 5.7 °C | 27.94 mm |
| April | -3.2 °C | 11.1 °C | 27.18 mm |
| May | 1.2 °C | 16.4 °C | 36.32 mm |
| June | 4.3 °C | 21.4 °C | 36.07 mm |
| July | 7.9 °C | 27.8 °C | 17.27 mm |
| August | 7.3 °C | 27.1 °C | 19.05 mm |
| September | 3.5 °C | 21.5 °C | 20.32 mm |
| October | -2.1 °C | 13.7 °C | 24.89 mm |
| November | -8.4 °C | 4.7 °C | 20.83 mm |
| December | -13.7 °C | -1.8 °C | 37.59 mm |
| Annual | -3.2 °C | 12.2 °C | 324.36 mm |
| Average First Frost Date | Aug. 21 - Aug. 31 |
| Average Last Frost Date | Jun. 1 - Jun. 10 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |