Highest temperature in Seattle on August 16?

Platform comparison

Market context

Seattle's weather on 16 August 2026 will determine the settlement range for this market, with the highest temperature recorded at Sea-Tac Airport serving as the resolution metric. The current 0% probability suggests traders are pricing in either exceptionally cool conditions or uncertainty about the market mechanics themselves, given that August typically produces measurable heat in the Pacific Northwest.

Historical August temperatures at Seattle-Tacoma International Airport show a median high around 79°F, with records reaching into the low 90s during heat waves. The 1994 heat dome produced 96°F in Seattle, whilst more recent Augusts have remained closer to seasonal norms. August 2021 saw a significant heat event across the region, though Seattle itself remained below 90°F. This baseline matters because the market's 0% reading appears disconnected from typical August variability—even cool years produce highs in the mid-70s to low 80s range.

Traders should monitor late July and early August 2026 weather patterns, particularly ridge positioning over the Pacific Northwest and any developing heat systems. The National Weather Service's extended forecasts become more reliable roughly two weeks prior to the settlement date. Sea-Tacoma's elevation and maritime influence create a moderating effect compared to inland locations, which historically caps extreme heat. The specific reliance on Weather Underground's Daily Observations table rather than summary figures introduces a technical dependency worth verifying before settlement approaches.

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

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

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 Prediction Today. 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.

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%.