The official National Weather Service forecast for Zionsville — 39.9509°N, 86.2619°W, 4.2 miles from I-65. Forecasts here are written by NWS IND, this county’s forecast office.
| Boone County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 34 | 39 | 50 | 63 | 73 | 81 | 83 | 82 | 78 | 65 | 51 | 39 | 62 |
| Avg low °F | 19 | 22 | 31 | 40 | 51 | 60 | 63 | 61 | 54 | 43 | 33 | 24 | 42 |
| Precip in | 2.8 | 2.5 | 3.2 | 4.2 | 4.6 | 4.9 | 4.3 | 3.3 | 3.0 | 3.3 | 2.8 | 2.9 | 41.8 |
1996–2025 normals for Boone County — the climate division Zionsville sits in. All-time county record high 101.9°F (1954-07-15); record low -25.7°F (1994-01-19). Source: NOAA / National Weather Service.