The official National Weather Service forecast for Gray Summit — 38.4898°N, 90.8168°W, 1.5 miles from I-44. Forecasts here are written by NWS LSX, this county’s forecast office.
| Franklin County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 41 | 46 | 58 | 68 | 77 | 85 | 89 | 87 | 81 | 70 | 57 | 45 | 67 |
| Avg low °F | 21 | 25 | 34 | 43 | 53 | 62 | 66 | 64 | 56 | 45 | 34 | 26 | 44 |
| Precip in | 2.6 | 2.4 | 3.7 | 4.7 | 4.8 | 4.2 | 4.3 | 3.9 | 3.2 | 3.2 | 3.1 | 2.5 | 42.6 |
1996–2025 normals for Franklin County — the climate division Gray Summit sits in. All-time county record high 110.9°F (1954-07-14); record low -21.3°F (1989-12-23). Source: NOAA / National Weather Service.