The official National Weather Service forecast for Spearfish — 44.4908°N, 103.8594°W, population 13,206, 2 miles from I-90.
| Lawrence County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 36 | 36 | 45 | 52 | 62 | 74 | 82 | 80 | 72 | 57 | 45 | 36 | 56 |
| Avg low °F | 13 | 12 | 20 | 28 | 37 | 47 | 54 | 52 | 43 | 31 | 21 | 14 | 31 |
| Precip in | 1.0 | 1.2 | 1.4 | 2.8 | 4.2 | 3.4 | 2.7 | 2.3 | 1.8 | 2.1 | 1.0 | 1.0 | 24.9 |
1996–2025 normals for Lawrence County — the climate division Spearfish sits in. All-time county record high 101.6°F (2006-07-29); record low -34.4°F (2024-01-14). Source: NOAA / National Weather Service.