Highest temperature in Seattle on August 9?

Platform comparison

Market context

Polymarket is pricing this Seattle temperature contract at **0% YES**, even though the event itself is straightforward: the highest temperature recorded at Seattle–Tacoma International Airport on 9 August 2026. On Polymarket, traders hold USDC on Polygon and buy conditional tokens tied to the temperature band that matches the final Weather Underground Daily Observations reading, so the key is the recorded airport high rather than any broader citywide impression or headline forecast.[1][6]

That zero bid is easiest to read against the historical and comparable context for Seattle in August, when highs commonly sit in the upper 70s Fahrenheit. Weather Underground’s historical market page for the same date already shows a 77°F daily maximum at KSEA, while third-party weather archives for 9 August 2026 also put the day’s high around the mid- to upper-70s, underscoring that the market’s 0% print is a data artefact rather than a statement that the temperature was impossible.[1][4][8][9]

For traders, the main catalyst is not a forecast update but the settlement source itself: Weather Underground’s Daily Observations table for KSEA, which can still be revised until the first datapoint for 10 August appears.[1] That means the practical watchlist is the final posted observation, any late data correction on Wunderground, and whether an alternate reporting source such as the National Weather Service confirms the same airport maximum; the market settles by the Wunderground table, so the on-chain outcome depends on that single data feed.[1][2]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in Seattle on August 9? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Kalshi UK, which mirrors the Polymarket order book at 0% fees.

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

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.

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%.