The official National Weather Service forecast for White River — 43.568°N, 100.7454°W, 21.9 miles from I-90.
| Mellette County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 34 | 38 | 49 | 59 | 70 | 81 | 89 | 87 | 79 | 63 | 49 | 37 | 61 |
| Avg low °F | 13 | 15 | 24 | 33 | 44 | 55 | 62 | 59 | 50 | 37 | 25 | 15 | 36 |
| Precip in | 0.5 | 0.6 | 1.1 | 2.4 | 3.4 | 3.2 | 2.5 | 2.3 | 1.7 | 1.6 | 0.5 | 0.6 | 20.4 |
1996–2025 normals for Mellette County — the climate division White River sits in. All-time county record high 111.9°F (2006-07-16); record low -28.4°F (1983-12-23). Source: NOAA / National Weather Service.