Recent forecasts from the National Weather Service and private models indicate highs near 88–91°F for Chicago on August 31, driven by southwest winds advecting warmer, more humid air ahead of building high pressure and a modest warming trend from recent 80s readings. Partial morning cloudiness is expected to give way to partly sunny skies, supporting afternoon heating, while dew points in the upper 60s to low 70s and light winds limit extreme mixing. Minor model spread arises from subtle differences in cloud cover and timing of any weak disturbances, keeping probabilities concentrated on 88–93°F bins as traders incorporate the latest guidance and historical late-August climatology near 82°F.