Official National Weather Service observations at Chicago O'Hare International Airport (KORD)—the market's authoritative station—recorded a maximum temperature of 58-59°F on May 7, driving trader consensus to a 100% implied probability for that outcome, as verified by automated surface weather observations peaking in the early afternoon under partly cloudy skies. This positioning reflects the dominance of a cool mid-level air mass from a recent Canadian front and persistent upper-level troughing over the Midwest, which suppressed highs well below the climatological May 7 normal of 67°F following May 6's even chillier 56-57°F readings amid light west-northwest winds of 5-10 mph. While resolved with strong evidentiary support from NOAA data, rare challenges could arise from post hoc measurement revisions or disputes over peak-hour sensor readings, though such adjustments are exceedingly uncommon for standard daily maxima.