| 2023 Hardiness Zone: | Zone 7b: 5°F to 10°F Zone 7a: 0°F to 5°F |
| 2012 Hardiness Zone: | Zone 7a: 0°F to 5°F |
| 1990 Hardiness Zone: | Zone 6b: -5F to 0F |
| Average First Frost Date: | Nov. 1 - Nov. 10 |
| Average Last Frost Date: | Apr. 11 - Apr. 20 |
| Koppen-Geiger Climate Zone: | Cfa - Humid Subtropical Climate |
| Ecoregion: | 71e - Western Pennyroyal Karst Plain |
| Heat Zone Days: | 46 - 60 days Over 86°F |
Annual Climate Data for ZIP Code 37148 - Portland, TN | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 26 | 29 | 37 | 46 | 56 | 64 | 68 | 66 | 59 | 47 | 39 | 29 | 47 |
| Avg Max Temp (°F) | 43 | 48 | 59 | 68 | 76 | 84 | 88 | 87 | 81 | 70 | 58 | 47 | 68 |
| Avg Precip (In.) | 4.16 | 4.13 | 5.43 | 4.2 | 5.43 | 4.57 | 4.4 | 3.47 | 3.78 | 3.31 | 4.66 | 5.04 | 52.59 |