Letha, Idaho has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 39 °F (low) to 64.8 °F (high). Annual precipitation averages 10.6 Inches. 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 | 23.3 °F | 37.7 °F | 1.35 in. |
| February | 26.6 °F | 46.0 °F | 0.9 in. |
| March | 32.1 °F | 56.8 °F | 1.12 in. |
| April | 37.0 °F | 64.1 °F | 0.95 in. |
| May | 45.4 °F | 73.4 °F | 1.26 in. |
| June | 52.1 °F | 81.7 °F | 0.75 in. |
| July | 58.8 °F | 92.5 °F | 0.25 in. |
| August | 56.4 °F | 91.1 °F | 0.16 in. |
| September | 47.6 °F | 80.7 °F | 0.44 in. |
| October | 37.1 °F | 65.9 °F | 0.75 in. |
| November | 28.7 °F | 49.4 °F | 1.06 in. |
| December | 23.4 °F | 38.6 °F | 1.57 in. |
| Annual | 39 °F | 64.8 °F | 10.56 in. |
| 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 : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |