Highest temperature in Seattle on August 9?

Platform comparison

Market context

Polymarket is pricing this Seattle airport temperature contract at **0% YES**, which implies the crowd sees no meaningful chance the official Weather Underground daily observations table will land in the specified outcome range. On Polymarket, traders are buying and selling USDC-settled conditional tokens on Polygon, so the quoted price reflects a live consensus rather than a fixed forecast. The market resolves from the **Seattle-Tacoma International Airport Station** on Weather Underground, and the daily observations table controls if it differs from any summary high. [3][4]

That 0% reading sits against a historical backdrop in which Seattle’s August highs are usually modest by US standards, but short warm spells can still push the airport into the upper 70s or low 80s. The Weather Service’s Seattle climate report shows a normal August maximum of **79°F** and a record maximum of **98°F**, while recent August observations include highs of **83°F** on one day and **88°F** on 6 August in 2026, showing that the distribution is not tightly clustered even in a marine climate. That matters for Polymarket because the market is not asking whether Seattle is generally warm; it is asking for one day’s realised airport high, which can hinge on a few degrees of afternoon heating. [2][13]

For traders, the main catalysts are the forecast trend into the relevant day, the strength of onshore flow off the Pacific, and whether cloud cover suppresses daytime mixing at Sea-Tac. Weather Underground’s own historical daily readings are the settlement reference, and Polymarket says revisions remain relevant only until the first datapoint for the following date appears, so late data handling can matter at the margin. The current market page already shows the contract heavily concentrated in the **76–77°F** band, which suggests the crowd is anchoring to a cool-summer baseline rather than a heat spike. [3][4]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

Resolution & payout

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

FAQ

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is PolyGram. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like PolyGram trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.