Traders assign near-certainty to an 80-81°F high at Seattle-Tacoma International Airport on August 4 because official National Weather Service observations recorded that exact peak under a building upper-level ridge, sunny skies, light northerly flow, and minimal smoke interference. This aligns with climatological norms for early August in the Puget Sound region, where daily maxima typically range from the mid-70s to low-80s absent strong marine intrusions or heat domes. Model consensus from the prior 48 hours consistently projected this narrow band, with limited spread across ensembles. Only an unforecasted surge in onshore flow or station-specific microclimate effects could have shifted the outcome outside this bin, scenarios rendered improbable by real-time surface and upper-air data.