National Weather Service forecasts and model consensus point to a Seattle high near 74–75°F on August 23, aligning with the market’s leading 58.5% implied probability for that bin. Persistent morning marine-layer stratus under light southwesterly onshore flow limits daytime insolation and caps warming several degrees below the 77°F August normal, while preventing offshore ridging that could push readings into the upper 70s. Recent upper-level trough passage has maintained this moderate regime, with gradual afternoon clearing insufficient for significant further temperature rise. Traders have weighted the outcome heavily toward 72–77°F bins because ensemble guidance shows little spread around this marine-influenced value, though any earlier dissipation of the stratus could nudge readings modestly higher before sunset.