Highest temperature in Seattle on August 9?

Platform comparison

Market context

Seattle’s highest temperature on 9 August 2026 will be set by the Weather Underground daily observations for Seattle-Tacoma International Airport, not the site’s summary high/low panel, so a programmatic check needs to read the hourly or daily observations table and wait for the final post-midnight update before treating the number as settled.[3] In practical terms, the market is a single-day airport-station temperature range event rather than a citywide forecast, which matters because a coastal marine layer or late-afternoon onshore breeze can cap the reading even when inland parts of the region feel warmer.[3][8]

For context, Seattle’s August climatology is modest by US standards: the normal maximum temperature is about 79°F, and recent August days often land in the upper 70s or low 80s rather than the 90s.[2][1] That framing makes the current 0% YES crowd price look like an obvious disconnect only if the market’s bracket is above the likely observed range; on the more common outcome path, traders typically key off whether the airport tops out in the 74-77°F band or prints a slightly warmer late-day excursion before the sea breeze returns.[1][2]

A hands-on trader would watch the National Weather Service forecast cycle, especially the Seattle forecast discussions and the 7-day point forecast, alongside any late revisions in the Weather Underground observation feed for KSEA.[5][8][3] The main catalysts are simple but time-sensitive: cloud cover breaking earlier than expected, offshore flow, or a stronger-than-forecast marine push can move the high by a couple of degrees, which is enough to shift the relevant temperature band in a tightly binned market.[8][3]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in Seattle on August 9? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

UK Frequently Asked Questions

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 Polymarket Review UK. 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.

Is Polymarket legal in the UK?

Polymarket is accessible to UK traders but is not UKGC-licensed. It operates under US CFTC jurisdiction. UK residents face no domestic legal prohibition on using it, but UKGC consumer protections do not apply. For UKGC-regulated alternatives, Betfair Exchange and Smarkets offer similar prediction-style markets.

Do I pay tax on prediction market profits in the UK?

UKGC-licensed platform profits (Betfair, Smarkets) are typically tax-free gambling winnings for UK individuals. Polymarket profits involve USDC crypto transactions, which HMRC treats as Capital Gains Tax events. Keep full transaction records and report via Self Assessment if gains exceed £3,000 per tax year.

How do I deposit on Polymarket from the UK?

UK traders typically fund Polymarket via Coinbase UK, Kraken or Revolut — buying USDC with GBP and transferring to a Polygon-compatible wallet (MetaMask, Coinbase Wallet). Polymarket's onboarding walks you through the bridging process. Typical GBP-to-USDC conversion costs 0.5–1%.