Highest temperature in Seattle on August 9?

Platform comparison

Market context

Seattle’s late-summer temperature can still surprise, but the setup for 9 August has been modest rather than extreme: forecast and observed outputs around the event cluster in the mid-70s Fahrenheit, with AccuWeather showing 76°F/57°F and Weather Underground’s monthly history page indicating 8/9/2026 data near 68°F in its summary view, while the market itself settles on the highest reading in the Daily Observations table at Sea-Tac, not the headline high/low box.[1][10][14][15] That distinction matters because the contract is sensitive to the single warmest hourly or sub-hourly observation captured at Seattle-Tacoma International Airport, and the settlement window remains open until the first datapoint for the following day is published, allowing late-day revisions to count if they appear before that cut-off.[7]

The 0% crowd-implied YES price is easier to read against Seattle’s August climatology than as a literal statement about the weather. Sea-Tac’s normal maximum for 9 August is around 79°F, and the historical record for that date is 99°F, so the market is effectively pricing in a day well below the extreme tail of the distribution.[4][6][12] Comparable August events show that Seattle can reach the 90s during regional heat episodes, but those outcomes are usually tied to broader western Washington heat waves rather than a routine maritime flow day.[8][18]

For traders, the main catalyst is not an on-chain event but whether Sea-Tac’s observed afternoon peak prints above the forecast band, since the contract settles in USDC and therefore tracks the exact temperature bucket rather than a directional weather narrative. On crypto venues, the relevant backdrop is whether BTC and ETH risk appetite is stable enough to keep prediction-market liquidity tight; if funding is elevated or spot volatility is rising, marginal weather positions can move less efficiently, but no specific macro trigger is currently more important than the official observation feed itself. The practical watchpoint is the Weather Underground Daily Observations update cycle and any late revision before the next day’s first entry, because that is what determines the final bucket.[7][13]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reads Highest temperature in Seattle on August 9? on-chain. Polymarket's quote comes directly from the Polygon order book — the only comparable venue with on-chain settlement. Kalshi (USD, off-chain), Betfair (GBP/EUR, off-chain) and Manifold (play-money) are listed alongside for venue context. Every CTA routes to BTC Prediction, which mirrors the Polymarket order book directly.

Resolution & payout

Settlement is on-chain via UMA Optimistic Oracle. A proposer posts the outcome with a bond, a two-hour dispute window opens, then the smart contract lifts winning conditional tokens to 1 USDC and sends payments to holders' wallets automatically. No withdrawal fees beyond Polygon gas.

Off-chain venues (Kalshi, Betfair, Smarkets) settle in local fiat through bank-side clearing — faster than SWIFT, slower than on-chain. Manifold pays no real cash.

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