The official National Weather Service forecast for Bethlehem — 44.2803°N, 71.6881°W, 2.7 miles from I-93.
| Grafton County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 27 | 31 | 39 | 52 | 65 | 73 | 78 | 76 | 70 | 56 | 43 | 33 | 54 |
| Avg low °F | 8 | 10 | 18 | 29 | 40 | 50 | 55 | 53 | 46 | 36 | 26 | 16 | 32 |
| Precip in | 3.2 | 2.8 | 3.3 | 3.8 | 4.2 | 5.0 | 4.9 | 4.2 | 3.8 | 4.9 | 3.6 | 4.3 | 48.0 |
1996–2025 normals for Grafton County — the climate division Bethlehem sits in. All-time county record high 94.4°F (1975-08-03); record low -34.2°F (1957-01-14). Source: NOAA / National Weather Service.