The official National Weather Service forecast for Helena — 46.5927°N, 112.0361°W, population 52,380, 1.9 miles from I-15.
| Lewis and Clark County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 33 | 33 | 42 | 50 | 59 | 67 | 79 | 77 | 67 | 52 | 40 | 32 | 53 |
| Avg low °F | 16 | 15 | 22 | 28 | 35 | 42 | 49 | 47 | 40 | 31 | 23 | 16 | 30 |
| Precip in | 1.6 | 1.8 | 1.6 | 2.0 | 2.9 | 2.8 | 1.1 | 1.3 | 1.5 | 1.7 | 1.7 | 1.9 | 21.9 |
1996–2025 normals for Lewis and Clark County — the climate division Helena sits in. All-time county record high 96.5°F (2002-07-13); record low -38.1°F (2024-01-14). Source: NOAA / National Weather Service.