Lowest temperature in Hong Kong on August 8?

Platform comparison

Market context

Polymarket is pricing this contract at **0% YES**, so the chain is effectively treating a sub-bracket low in Hong Kong as a dead outcome for now, even though the event will only settle once the Hong Kong Observatory publishes the final “Absolute Daily Min” for 8 August in its Daily Extract. The market uses USDC on Polygon and conditional tokens, so there is no need to wait for a headline forecast; the only thing that matters is the Observatory’s final verified figure in degrees Celsius, to one decimal place.

Historically, Hong Kong’s August nights are warm rather than cool. The Hong Kong Observatory’s 1991–2020 normals put 8 August at a mean minimum of 26.9°C, with mean temperature 29.0°C and mean maximum 31.7°C, which is a useful anchor for reading the distribution of likely settlement bands.[1] Recent August summaries also show that monthly mean minimums have tended to sit well above the teens: August 2024 averaged 27.7°C and August 2025 averaged 27.0°C, despite very different rainfall patterns.[10][11] The lower-temperature tail exists in the historical record, but it is a long way from the August norm; that makes very low brackets hard to justify unless an unusual weather setup develops.[2][4]

For a trader, the main catalysts are the Observatory’s hourly readings, the afternoon evolution of rain and cloud, and whether a weather system drags cooler air or persistent showers over the territory before midnight. At 1 a.m. HKO reported 29°C at the Observatory, with several other urban stations still in the high 20s to 30°C range, which is consistent with a warm floor early in the day.[15] The key dependency is the final Daily Extract publication, because the market cannot resolve until the official daily minimum is posted there.[16]

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.

UK Frequently Asked Questions

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.

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%.