Highest temperature in Shanghai on August 20?

Platform comparison

Market context

Shanghai's highest temperature on 20 August 2026 will be measured at Pudong International Airport Station and resolved against Weather Underground's Daily Observations table, with settlement occurring at midday UTC that day. The current Polymarket pricing reflects zero probability across all temperature bands, suggesting either minimal liquidity or genuine uncertainty about whether any outcome will trade meaningfully before the settlement window closes.

Historical August temperatures in Shanghai cluster between 32–35°C on average, with extremes occasionally reaching 37–38°C during heat waves. The city's subtropical monsoon climate produces consistent high-temperature days throughout summer, making mid-range outcomes (32–35°C) statistically the most frequent. Comparable August 2025 data would provide the most direct calibration, though multi-year averages from the China Meteorological Administration show that temperatures below 30°C or above 39°C in August remain rare events in Shanghai's modern record.

Traders monitoring this contract should track typhoon activity across the Western Pacific in early August 2026, as tropical systems can suppress temperatures significantly or, conversely, create humid heat domes that push readings higher. The China Meteorological Administration typically issues seasonal forecasts by late July, and any El Niño or La Niña conditions developing through 2026 will influence regional pressure patterns. Weather Underground's data feed from Pudong remains the sole authoritative source; discrepancies between its Daily Observations and Day High & Low summaries have historically favoured the granular observations table by 0.5–1.5°C in Shanghai's case.

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

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%.