The official National Weather Service forecast for Griswold — 41.235°N, 95.1375°W, 18.2 miles from I-80.
| Cass County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 31 | 36 | 49 | 62 | 72 | 82 | 85 | 83 | 77 | 65 | 50 | 36 | 61 |
| Avg low °F | 13 | 16 | 28 | 38 | 49 | 60 | 63 | 61 | 53 | 40 | 28 | 18 | 39 |
| Precip in | 0.8 | 1.1 | 1.9 | 3.3 | 5.3 | 5.0 | 3.7 | 4.4 | 3.2 | 2.8 | 1.6 | 1.2 | 34.3 |
1996–2025 normals for Cass County — the climate division Griswold sits in. All-time county record high 103.8°F (1974-07-22); record low -28.8°F (1974-01-12). Source: NOAA / National Weather Service.