The official National Weather Service forecast for Southport — 39.6651°N, 86.1278°W, 3.3 miles from I-65. Forecasts here are written by NWS IND, this county’s forecast office.
| Marion County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 36 | 40 | 52 | 64 | 73 | 82 | 84 | 83 | 78 | 66 | 52 | 40 | 62 |
| Avg low °F | 20 | 23 | 32 | 41 | 52 | 62 | 65 | 63 | 55 | 44 | 33 | 25 | 43 |
| Precip in | 3.0 | 2.6 | 3.5 | 4.5 | 4.7 | 5.1 | 4.1 | 3.3 | 3.2 | 3.3 | 2.9 | 3.1 | 43.3 |
1996–2025 normals for Marion County — the climate division Southport sits in. All-time county record high 103.1°F (2012-06-29); record low -25.5°F (1994-01-19). Source: NOAA / National Weather Service.