Trader sentiment for Seattle's September 2026 precipitation centers on accumulated totals near the long-term average of about 1.6 inches at Sea-Tac, with the market's tight clustering around 1-2 inches reflecting mostly dry conditions through late September and only modest rain expected in the final days. Persistent high pressure and limited frontal activity have kept measurable precipitation low since early month, aligning with typical late-summer patterns before the fall transition. Remaining uncertainty stems from potential weak systems that could add 0.2-0.5 inches, pushing totals into the 1.5-2 inch bin versus staying under 1.5 inches. Official NWS forecasts and model consensus on steering patterns will determine resolution as the month closes.