St. Clair County, Illinois
Local growing conditions for St. Clair County: the USDA hardiness zones found here, frost dates, and live weather for communities across the county. Based on 27 ZIP codes in our data.
Hardiness zones in St. Clair County
St. Clair County spans these USDA plant hardiness zones (by number of ZIP codes):
Local weather & frost dates
Open any community in St. Clair County for its live forecast, frost dates, and planting calendar:
Cahokia Heights 62206
Brooklyn 62059
East St. Louis 62201
East St. Louis 62203
Washington Park 62204
East St. Louis 62205
Cahokia Heights 62207
Fairview Heights 62208
Belleville 62220
Shiloh 62221
Belleville 62223
Scott AFB 62225
Swansea 62226
Caseyville 62232
Cahokia Heights 62239
Dupo 62240
Freeburg 62243
Lebanon 62254
Lenzburg 62255
Marissa 62257
Mascoutah 62258
Millstadt 62260
New Athens 62264
O'Fallon 62269
More for Illinois
- Agriculture in Illinois
- Frost dates across Illinois
- USDA hardiness zones explained
- Planting calendar by ZIP code
County growing conditions are compiled from our ZIP-code database, USDA hardiness-zone data, and NOAA climate normals. Conditions vary within a county by elevation and local microclimate. Page updated Aug 4, 2026.