The official National Weather Service forecast for Blountville — 36.5332°N, 82.3268°W, 1 miles from I-81.
| Sullivan County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 46 | 51 | 60 | 70 | 77 | 84 | 86 | 85 | 81 | 70 | 59 | 50 | 68 |
| Avg low °F | 26 | 30 | 36 | 43 | 52 | 60 | 64 | 63 | 57 | 45 | 35 | 30 | 45 |
| Precip in | 3.8 | 3.9 | 3.9 | 4.1 | 4.2 | 4.0 | 5.0 | 4.0 | 3.2 | 2.8 | 3.0 | 3.8 | 45.7 |
1996–2025 normals for Sullivan County — the climate division Blountville sits in. All-time county record high 101.7°F (2012-06-30); record low -15.9°F (1985-01-22). Source: NOAA / National Weather Service.