Official National Weather Service guidance for Chicago on September 26 points to a high near 67°F under mostly sunny conditions with light east-southeast winds around 5 mph, consistent with other model outputs showing upper 60s. This places the expected peak near the boundary between the two leading market buckets, where traders balance potential afternoon warming from clear skies against moderating influences from Lake Michigan and a cool easterly flow. Historical climatology shows an average high of about 72°F, but the current pattern favors below-normal readings. Minor shifts in cloud timing or local observations could alter the exact maximum, with updated NWS briefings and model runs providing the next key data points before resolution.