Official National Weather Service observations at Seattle-Tacoma International Airport recorded a daily maximum of 74°F on September 8, 2026, matching the seasonal normal of 74°F and falling well below the all-time September 8 record of 86°F set in 1943. Clear skies, light northerly winds, and typical late-summer atmospheric conditions produced this moderate high, with no heat advection or subsidence supporting warmer readings. Market-implied odds reflect verified station data resolving squarely in the 74-75°F bin. Minor discrepancies between airport and urban stations or slight timing differences in peak measurement could theoretically shift resolution, though official climatological summaries confirm the outcome with high confidence.