The official National Weather Service forecast for Plymouth — 41.9584°N, 70.6673°W, 12.6 miles from I-495.
| Plymouth County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 39 | 41 | 48 | 58 | 68 | 77 | 83 | 81 | 75 | 63 | 53 | 44 | 61 |
| Avg low °F | 22 | 23 | 29 | 38 | 48 | 57 | 64 | 62 | 55 | 44 | 35 | 27 | 42 |
| Precip in | 4.4 | 3.8 | 5.1 | 4.6 | 4.0 | 3.9 | 3.4 | 3.8 | 4.3 | 5.2 | 4.0 | 4.8 | 51.3 |
1996–2025 normals for Plymouth County — the climate division Plymouth sits in. All-time county record high 99.6°F (2025-06-25); record low -10.5°F (1957-01-15). Source: NOAA / National Weather Service.