**An incoming Pacific storm system is the dominant driver suppressing Seattle's high temperature on September 2, 2026, to levels below the early-September climatological average of roughly 74°F.** Official forecasts from sources such as the National Weather Service and private models highlight widespread cloud cover, periods of rain (with totals of 0.1–0.5 inches possible), and southerly winds of 10–15 mph with gusts to 25 mph, all of which limit daytime heating. These conditions produce a consensus range centered on the mid-to-upper 60s, with most guidance showing highs from the mid-60s to lower 70s depending on the exact timing and intensity of precipitation and cloud breaks. Model consensus and recent observations of the approaching low-pressure system explain why the market clusters tightly around 66–69°F (collectively over 67% implied probability). Key differentiating variables include the degree of solar insolation through morning partial clearing versus afternoon rain-cooled air masses, plus minor steering-pattern shifts that could allow slightly warmer or cooler advection. Historical analogs for similar early-September storms show highs frequently 5–10°F below average, aligning with the current forecast spread and the modest probabilities assigned to outcomes outside 64–71°F. Updated model runs and National Weather Service briefings through the afternoon of September 1 will provide the next resolution-relevant data points.