| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 8a: 10°F to 15°F Zone 7b: 5°F to 10°F Zone 7a: 0°F to 5°F |
| 2012 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7b: 5°F to 10°F Zone 7a: 0°F to 5°F |
| 1990 Hardiness Zone: | Zone 6b: -5F to 0F |
| Average First Frost Date: | Oct. 11 - Oct. 20 |
| Average Last Frost Date: | May 11 - May 20 |
| Koppen-Geiger Climate Zone: | BSk - Cold Semi-Arid Climate |
| Ecoregion: | 10l - Lower Snake and Clearwater Canyons |
| Heat Zone Days: | 31 - 45 days Over 86°F |
Annual Climate Data for ZIP Code 83501 - Lewiston, ID | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 28 | 31 | 35 | 40 | 46 | 53 | 58 | 58 | 50 | 41 | 34 | 28 | 42 |
| Avg Max Temp (°F) | 39 | 46 | 53 | 61 | 70 | 78 | 87 | 87 | 76 | 62 | 47 | 39 | 62 |
| Avg Precip (In.) | 1.12 | .84 | 1.13 | 1.14 | 1.41 | 1.03 | .69 | .67 | .75 | .91 | 1.17 | 1.01 | 11.87 |