Highest temperature in Beijing on August 4?

Platform comparison

Market context

Beijing Capital International Airport’s top reading for 4 August will come from a single-day airport observation, so the relevant number is the day’s **maximum at ZBAA**, not the citywide average or a forecast low. In practical terms, a programme reading this market would poll the Wunderground history page for the airport, convert to Celsius if needed, and wait for the final daily high before mapping it to the market’s outcome bands.

The current 0% YES price is hard to reconcile with the meteorological baseline. Multiple August forecasts for Beijing show daytime highs in the low-to-mid 30s Celsius, with one daily forecast giving around **36°C** and others clustering around **31–34°C**; climatology sources also describe August as hot, humid, and often rainy, which still leaves room for a high well above the lowest bands. Beijing’s airport station can differ from city forecasts, but a zero-implied chance suggests the market is pricing in an extreme outcome mismatch, a late data issue, or a band that is far above the expected top reading.

For traders automating around this event, the main catalysts are the final afternoon warmth, convective showers, and any aviation-specific weather that caps the airport maximum earlier than the broader city forecast would imply. The useful dependency is the resolution source itself: if the Wunderground daily page updates the high after the first published datapoint for the following day, that finalised value becomes the settlement anchor, so bots and conditional orders should keep checking until the cutoff rather than assuming an early reading is definitive.

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.

FAQ

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 Polymarket Bot UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Polymarket Bot UK trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.