The official National Weather Service forecast for Johnston — 41.8219°N, 71.5067°W, 4.4 miles from I-95.
| Providence County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 37 | 40 | 47 | 59 | 69 | 77 | 82 | 81 | 74 | 63 | 52 | 42 | 60 |
| Avg low °F | 20 | 21 | 28 | 37 | 47 | 57 | 63 | 61 | 54 | 43 | 33 | 26 | 41 |
| Precip in | 4.2 | 3.6 | 4.7 | 4.6 | 4.0 | 4.3 | 3.8 | 3.8 | 4.4 | 5.1 | 3.8 | 5.0 | 51.3 |
1996–2025 normals for Providence County — the climate division Johnston sits in. All-time county record high 98.8°F (2025-06-25); record low -13.6°F (1984-01-22). Source: NOAA / National Weather Service.