Official National Weather Service observations from Seattle-Tacoma International Airport recorded a daily maximum of 70°F on September 5, 2026—five degrees below the 1991–2020 normal of 75°F—while nearby reports ranged 70–74°F amid stable high pressure, light winds, and minimal cloud cover that limited daytime heating. These verified measurements, released in post-event climate summaries, align closely with the narrow 68–69°F bin and explain the market’s near-certain 100% implied probability. Minor station-to-station differences or final data revisions represent the only realistic pathways that could shift resolution outside this range, though such adjustments are historically rare once preliminary values are confirmed.