Official measurements from NOAA stations in Seattle recorded total September 2026 precipitation between 1.5 and 2 inches, aligning precisely with the market’s near-certain outcome. This range matches long-term climatological averages for the month, when the Pacific Northwest typically experiences transitional autumn patterns with moderate rainfall from weakening summer highs and early frontal systems. Model consensus and real-time observations throughout September supported steady accumulation without extreme events, reinforcing trader confidence. Minor adjustments in gauge data or boundary definitions remain possible but would require substantial revisions unlikely to shift the result outside this narrow band.