The official National Weather Service forecast for Mountain City — 36.4746°N, 81.8048°W, 20.3 miles from I-81.
| Johnson County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 43 | 47 | 55 | 65 | 72 | 78 | 81 | 80 | 75 | 65 | 55 | 47 | 64 |
| Avg low °F | 24 | 27 | 32 | 40 | 48 | 56 | 60 | 59 | 52 | 42 | 32 | 27 | 42 |
| Precip in | 4.2 | 4.0 | 3.8 | 4.7 | 5.1 | 4.5 | 5.7 | 4.5 | 3.8 | 3.3 | 3.4 | 4.0 | 51.0 |
1996–2025 normals for Johnson County — the climate division Mountain City sits in. All-time county record high 95.4°F (2012-06-30); record low -20.5°F (1985-01-21). Source: NOAA / National Weather Service.