Letha, Idaho has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 3.9 °C (low) to 18.2 °C (high). Annual precipitation averages 268.2 Millimeters. Letha is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.8 °C | 3.2 °C | 34.29 mm |
| February | -3 °C | 7.8 °C | 22.86 mm |
| March | 0.1 °C | 13.8 °C | 28.45 mm |
| April | 2.8 °C | 17.8 °C | 24.13 mm |
| May | 7.4 °C | 23 °C | 32 mm |
| June | 11.2 °C | 27.6 °C | 19.05 mm |
| July | 14.9 °C | 33.6 °C | 6.35 mm |
| August | 13.6 °C | 32.8 °C | 4.06 mm |
| September | 8.7 °C | 27.1 °C | 11.18 mm |
| October | 2.8 °C | 18.8 °C | 19.05 mm |
| November | -1.8 °C | 9.7 °C | 26.92 mm |
| December | -4.8 °C | 3.7 °C | 39.88 mm |
| Annual | 3.9 °C | 18.2 °C | 268.22 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |