Highest temperature in Seattle on August 9?

Platform comparison

Market context

Seattle’s early-August heat has eased into a more typical marine influence, and the latest read-through points to a modest daytime ceiling rather than any late surge. Weather Underground’s primary settlement source already shows Seattle–Tacoma International Airport reached 77°F on 9 August, which sits inside the 76–77°F band now carrying the market’s full crowd weight; that makes the “now” question less about direction than about whether the final daily observation is locked in.[3][6]

The relevant historical frame is simple: Seattle’s August normals at Sea-Tac are around 79°F for the daily maximum, while nearby official climate records show that 9 August has reached 99°F in the past and 83°F yesterday, so the location can still vary meaningfully from one day to the next depending on onshore flow and cloud cover.[2] AccuWeather’s monthly outlook also had 9 August around the mid-70s, reinforcing that the market is sitting close to seasonal expectations rather than at an extreme.[1]

For traders, the main catalyst is not a forecast headline but the completeness of the Sea-Tac observation record on Weather Underground, because the market settles on the highest value in the Daily Observations table, not the summary high/low.[3] The key dependency is whether any late revision appears before the first datapoint for the following day is published; beyond that point, changes do not count for resolution.[3]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in Seattle on August 9? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Prediction Today, which mirrors the Polymarket order book at 0% fees.

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