Highest temperature in Guangzhou on August 21?

Platform comparison

Market context

Guangzhou's maximum temperature on 21 August 2026 will be measured at Baiyun International Airport Station and recorded in Weather Underground's Daily Observations table. The market currently prices this event at 0% across all temperature ranges, reflecting either extreme confidence in a specific outcome or minimal trading activity. Settlement depends on the precise figure logged in the primary data source rather than the Day High & Low summary section, a distinction that matters when Weather Underground's automated systems occasionally diverge between reporting tables.

Guangzhou experiences peak summer heat in late August, with historical August maxima typically ranging between 32–35°C. The 21st falls within the tail end of the summer monsoon season, when afternoon thunderstorms occasionally suppress peak temperatures by 2–3°C compared to drier spells. Reviewing August 2024 and 2025 data from Baiyun Station would establish the recent range; if previous years saw consistent readings above 33°C, the 0% probability on lower ranges becomes more interpretable as market consensus rather than genuine uncertainty.

Traders should monitor China Meteorological Administration forecasts released in the week preceding settlement, as tropical cyclone activity in the South China Sea can redirect moisture patterns and alter afternoon highs materially. The settlement window closes at 12:00 UTC on 21 August, giving traders roughly 12 hours after local midnight to react to overnight forecasts, though the actual temperature observation will be finalised by Weather Underground's automated station feed. Any technical outages at Baiyun Station or delays in data publication could affect resolution timing.

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

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.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

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%.