Will Seattle have between 2 and 2.5 inches of precipitation in September?

This market resolves Yes if total Seattle precipitation for September falls between 2.0 and 2.5 inches inclusive. September is a transition month in the Pacific Northwest: summer dryness gives way to autumn fronts, and the historical distribution of monthly totals is wide, with meaningful density precisely in the 2–2.5 inch band. The current 3.6% price implies the market sees this interval as unlikely, which conflicts with climatology.

Key drivers: Seattle's long-term September average is close to 1.6–1.7 inches, but the standard deviation is large, and years landing at 2–2.5 inches occur regularly — roughly 15–25% of the time in historical records. Our model assigns 22%, based on the distribution of monthly totals, seasonal timing and typical ENSO-neutral variability. The market is likely underpriced because of anchoring on 'dry Seattle' and thin liquidity in weather contracts.

For the outcome to win, one or two strong atmospheric fronts in mid-to-late September need to deliver 1.5–2 inches over a short window, with moderate rainfall the rest of the month. That is a standard pattern for the region.

Risks: a strong drought or persistent blocking anticyclone, or an unusually dry start to autumn. If September lands in the lower tail (under 1.5 inches) or, conversely, turns extremely wet (over 3 inches), the position loses.