**Trader sentiment for Seattle's September 2026 precipitation centers on the 1-1.5 inch bin (42.5% implied probability), consistent with the long-term climatological average of 1.6 inches at Sea-Tac.** Early-month observations through September 12 show only 0.47 inches accumulated, below normal, amid a pattern of ridging and limited troughing. National Weather Service short-term guidance indicates low precipitation probabilities after initial showers on the 13th, with mostly dry, sunny conditions favored through mid-month. Historical variability is high—many recent Septembers finished under 1 inch—yet late-month climatology supports additional rainfall. Model consensus and current steering patterns sustain the market's lean toward near-average totals while acknowledging forecast uncertainty in Pacific Northwest fall transition weather.