Recent National Weather Service and model guidance indicate a frontal system bringing clouds, showers, and easterly flow to Chicago through September 20, keeping overnight radiative cooling limited and supporting lows near 60–64 °F. Trader sentiment remains nearly evenly split between 53 °F or below and 72 °F or higher because forecast ensembles diverge on the exact timing of clearing and any late-period wind shift that could enhance or suppress minimum temperatures. Persistent cloud cover and precipitation favor milder readings by reducing longwave heat loss, while any earlier break in the overcast could allow greater cooling toward seasonal norms around 57 °F. Updated model runs and NWS briefings over the next 48 hours will clarify whether the low stays in the middle bins or shifts toward either tail.