Official National Weather Service forecasts for Seattle on September 28, 2026, indicate a daytime high near 65°F under mostly sunny to partly cloudy conditions, consistent with the market's heavy weighting toward the 66-67°F and 68-69°F bins. Recent observations show highs of 63-64°F over the prior two days amid a cooling trend late in the month, with light northerly winds and minimal precipitation risk supporting modest daytime warming. Late-September climatology places typical highs around 66°F, though model consensus and regional pressure patterns could allow slight upward revisions if afternoon insolation exceeds expectations. Key resolution thresholds hinge on official maximum temperature readings from Seattle-Tacoma International Airport, with updated model runs and morning briefings likely to refine the final outcome before markets close.