Highest temperature in Seattle on July 22?

Platform comparison

Market context

Seattle-Tacoma Airport has already run hot enough this week to leave the market leaning heavily towards the upper band: AccuWeather’s forecast for Wednesday pointed to a 91°F high, while WeatherSpark’s latest airport report late on 22 July showed 89.1°F with very dry air, a setup consistent with an afternoon peak already near or above the low 90s. That makes the current 0% price on the lower ranges look out of step with the day’s actual heat profile, especially if the airport station matched the broader Seattle-area warming seen elsewhere in the region.[5][3][1]

For context, Seattle’s late-July normals are much milder: the average high on 22 July is 77.5°F, and July highs typically sit in the mid-to-late 70s rather than the 90s.[2][6] The market description resolves to the highest temperature recorded at Seattle-Tacoma International Airport on 22 July, so comparable cases are the warmest airport observations on unusually hot summer days rather than citywide averages. Recent regional reporting also noted a western Washington heat spell with highs in the low 90s and “the hottest days of summer”, which is the sort of synoptic pattern that can push the airport station into the 90s even in a marine climate.[8][9]

The key catalysts are the day’s realised airport observations and whether afternoon clearing and inland high pressure were strong enough to sustain warming into the peak heating window. If the sea breeze arrived late, the airport could still print in the 90s; if marine influence strengthened earlier, the top reading would be capped lower despite the warm start. Traders should watch the final Wunderground history for KSEA, plus any late-breaking forecast adjustments from local outlets or the National Weather Service that changed the expected timing of cooling.[3][5][9]

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 Prediction Today. 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.

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.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.