Recent National Weather Service and ensemble forecasts for Chicago on October 4 point to mostly sunny skies with light west-to-northwest winds, supporting afternoon highs in the upper 60s to low 70s under stable high pressure. This consensus drives the tight clustering of market-implied odds around 72–75 °F, as traders weigh the exact peak against minor model spread in boundary-layer mixing and wind timing. Historical climatology places the Oct 4 average high near 68.5 °F, so current guidance reflects a modest warm anomaly. Resolution hinges on the official daily maximum at official stations, with limited upside risk from any unexpected cloud cover or earlier wind shift that could cap temperatures near 70 °F.