The official National Weather Service forecast for Lyman — 30.4947°N, 89.1256°W, 9.1 miles from I-10. Forecasts here are written by NWS LIX, this county’s forecast office.
| Harrison County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 61 | 65 | 72 | 77 | 84 | 89 | 91 | 91 | 87 | 80 | 70 | 64 | 78 |
| Avg low °F | 40 | 44 | 50 | 56 | 64 | 71 | 73 | 72 | 68 | 58 | 48 | 43 | 57 |
| Precip in | 4.9 | 4.5 | 5.2 | 5.7 | 5.3 | 7.0 | 7.2 | 6.7 | 5.4 | 3.4 | 3.6 | 5.2 | 64.1 |
1996–2025 normals for Harrison County — the climate division Lyman sits in. All-time county record high 104.1°F (2023-08-27); record low 6.6°F (1985-01-21). Source: NOAA / National Weather Service.