Mild southerly winds and mostly clear skies are supporting National Weather Service forecasts for overnight lows near 60°F across Chicago on October 9, aligning with the market's leading 54-55°F outcome at 47.5% implied probability. Recent model consensus shows limited overnight cooling after earlier northwest flow, with southerly advection maintaining above-normal readings despite typical early-October climatology near 49°F. Key variables include exact station minimums at O'Hare or Midway and any late-day adjustments from updated guidance, while lower-probability bins below 50°F reflect residual uncertainty in boundary-layer mixing and radiational cooling under calm conditions.