The official National Weather Service forecast for Topsham — 43.9276°N, 69.9759°W, 0.9 miles from I-295. Forecasts here are written by NWS GYX, this county’s forecast office.
| Sagadahoc County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 31 | 34 | 42 | 53 | 64 | 73 | 79 | 78 | 71 | 58 | 47 | 36 | 56 |
| Avg low °F | 13 | 15 | 24 | 34 | 44 | 53 | 60 | 58 | 51 | 41 | 30 | 21 | 37 |
| Precip in | 3.6 | 3.2 | 4.0 | 4.4 | 3.8 | 4.4 | 3.6 | 3.3 | 4.0 | 5.3 | 4.2 | 4.6 | 48.4 |
1996–2025 normals for Sagadahoc County — the climate division Topsham sits in. All-time county record high 101.7°F (1975-08-03); record low -22.1°F (1981-01-05). Source: NOAA / National Weather Service.