National Weather Service forecasts indicate a high near 71°F for Seattle on August 22 amid increasing clouds and a chance of showers tied to an approaching upper-level low. This pattern shift from recent sunny conditions introduces variability in solar heating and boundary-layer mixing, with marine air and precipitation timing likely capping peaks in the upper 60s to low 70s. Ensemble guidance shows modest spread around these values due to uncertain shower coverage and onshore flow strength, while climatological August averages near 75°F provide context but limited predictive weight given the active disturbance. The closely matched market probabilities around 66–73°F reflect this forecast uncertainty ahead of final observational data.