Highest temperature in Hong Kong on August 20?

Platform comparison

Market context

On 20 August 2026, the Hong Kong Observatory will record the day's highest temperature in degrees Celsius. Polymarket currently prices this contract at 0% YES, meaning traders are assigning negligible probability to any specific temperature band resolving. The settlement window closes at 12:00 UTC on that date, after which the Observatory's published daily maximum—recorded to one decimal place in their official Daily Extract—becomes binding. Until that data is finalised and published, the contract cannot resolve, creating a hard dependency on the Observatory's data release schedule.

Hong Kong's August climate is consistently hot and humid, with historical daily maxima typically ranging between 31°C and 34°C. The Observatory's records show that extreme heat days above 35°C occur occasionally but remain statistically uncommon in August; the territory's all-time August high stands at 36.3°C, set in 1990. Current pricing at 0% reflects the market's treatment of this as a conditional token contract awaiting outcome specification rather than genuine uncertainty about whether temperatures will be recorded.

Traders should monitor the Hong Kong Observatory's published forecasts in the week preceding 20 August 2026, as these typically indicate expected ranges with reasonable accuracy. Tropical cyclone activity during the season could materially affect daily maxima; the Observatory's typhoon warnings and track predictions will be the primary catalyst for repricing. The actual settlement hinges entirely on the Observatory's automated weather station network and their standard data validation procedures, with no discretionary interpretation involved in the final figure.

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 Kalshi 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%.