Traders assign the highest implied probability (39.5%) to a peak of 80–81°F in Chicago on July 19, reflecting National Weather Service model consensus for moderate high pressure and northwesterly flow limiting daytime heating. Recent ensemble runs show surface temperatures constrained by dew points in the mid-60s and limited southerly moisture advection, keeping maxima below the seasonal normal near 84°F. Secondary outcomes at 78–79°F (23%) and 82–83°F (21.5%) capture uncertainty in boundary-layer mixing and cloud cover timing, while probabilities drop sharply above 84°F due to the absence of strong warm advection in the latest guidance. Updated model cycles expected overnight will refine these ranges ahead of resolution.