Recent National Weather Service and private model guidance for Chicago points to a high in the upper 60s on September 27, cooler than the late-September climatological average near 72°F, amid persistent northeast flow and stable high pressure. Trader consensus clustering around 72–73°F (43.5% implied probability) and 74–75°F (21.5%) reflects expectations that guidance may trend warmer with the next model cycles, while the notable 20.5% on 78°F or higher captures residual uncertainty in the strength of any late-month warming. Lower bins remain discounted given the current cool anomaly and limited time for significant change before resolution.