Highest temperature in Seattle on August 10?

Platform comparison

Market context

Seattle’s highest temperature on 10 August 2026 was expected to land in the mid-70s Fahrenheit, which is consistent with the main crowd pricing on Polymarket, where the 74–75°F bucket led at 47% and 72–73°F sat next at 28%.[2] A separate sportsbook-style reference point also points lower than the contract’s zeroed-out crowd-implied stance: Robinhood’s event page was trading the Seattle daily temperature high around 73°F at 55¢, indicating a market consensus closer to a low-to-mid-70s outcome than to an extreme reading.[15] The current market probability of 0% YES is therefore a clear outlier versus both the platform crowd and the general weather forecast picture.[2][15]

For historical context, Seattle’s August 10 record high is 98°F, but the climatological centre of gravity is much lower: Extreme Weather Watch puts the average high for August 10 at 77.5°F, with the broader August mean high in Seattle in the upper 70s and the month’s all-time peak at 99°F.[5][16] That makes a mid-70s settlement the most natural analogue for this contract, while anything above 80°F would be materially warm relative to the date’s normal pattern.[5][16] In other words, the market is not pricing a record chase; it is pricing an ordinary summer day with a modest upside tail.[2][5]

Traders should watch the official Seattle-Tacoma International Airport observations that feed Weather Underground’s Daily Observations table, because the market resolves on that source rather than the headline Day High & Low summary.[11] Late-day warming, coastal cloud breaks, or a brief warm spell near the afternoon peak could still shift the final print by a degree or two, but the available forecasts for 10 August all sat close to 75°F with little precipitation risk.[12][18] The practical catalyst is therefore not a scheduled announcement, but the evolution of the day’s observed maximum at the airport station and whether it finishes in the 72–73°F, 74–75°F, or 76–77°F band.[11][12]

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 Kalshi vs Polymarket. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

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.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.