Highest temperature in Shenzhen on August 21?

Platform comparison

Market context

Shenzhen will experience peak summer heat on 21 August 2026, with the highest temperature recorded at Bao'an International Airport determining settlement. The market resolves to a specific temperature range based on the Daily Observations table from Weather Underground, which captures granular station data rather than the rounded summary figures displayed in the Day High & Low section. For programmatic traders, this distinction matters: automated systems querying Weather Underground's API must target the correct data table to avoid misalignment between expected and actual settlement values.

Historical August temperatures at Shenzhen Bao'an show consistent patterns. Over the past decade, peak daily highs in late August have ranged between 32–35°C, with occasional spikes to 36°C during particularly intense heat waves. The 0% crowd probability suggests traders are pricing in either extreme confidence in a specific temperature band or uncertainty about which range will actually resolve. Comparable markets on Chinese coastal cities during August typically see clustering around 33–34°C, providing a baseline for calibration.

Traders should monitor the Asian summer monsoon progression and any tropical cyclone activity in the South China Sea during mid-August 2026. Real-time tracking of atmospheric pressure systems and sea surface temperatures will signal whether conditions favour above-trend or below-trend highs. Weather Underground's station data updates hourly, allowing conditional orders to execute based on observed temperatures as they accumulate through the day—critical for markets settling on intraday extrema rather than closing values.

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

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.

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%.