Trader consensus for Chicago’s July 20 high clusters tightly around the 82–87 °F range because National Weather Service ensemble guidance shows moderate high pressure and northwesterly flow limiting daytime heating, with dew points in the mid-60s restricting moisture advection and boundary-layer mixing. This setup keeps maxima near or just below the July 20 climatological normal of 84.7 °F, producing the near-even split between the 84–85 °F and 86–87 °F bins while assigning sharply lower odds to 88 °F-plus outcomes. Recent model runs highlight lingering uncertainty in cloud-cover timing and subtle warm-air advection that could nudge readings a degree or two higher or lower, consistent with the balanced market pricing ahead of the final forecast updates on resolution day.