Highest temperature in Guangzhou on July 21?

Platform comparison

Market context

Guangzhou will experience peak summer heat on 21 July 2026, with the settlement hinging on the single highest temperature reading recorded at Baiyun International Airport throughout that calendar day. The resolution mechanism pulls directly from Wunderground's historical weather database, which logs hourly observations; traders will need to cross-reference the station's ICAO code (ZGGG) and confirm the Celsius toggle is active before settlement, as the platform defaults to Fahrenheit in some regions.

Guangzhou's July temperatures have historically clustered between 32–37°C, with extreme readings occasionally reaching 38–39°C during heat waves. The 0% crowd probability suggests either the market's upper temperature brackets are priced as implausible outliers, or liquidity remains sparse at the tails. Comparable July days at Baiyun show that readings above 35°C occur roughly 70% of the time; anything below 30°C would represent a significant weather anomaly for the season. Reviewing Wunderground's five-year historical archive for this station provides the empirical baseline needed to calibrate position sizing.

Traders automating this market should note that Wunderground updates its historical records with a lag of 24–48 hours post-settlement window closure. Any conditional order logic should account for this delay and verify the final reading against the official China Meteorological Administration data as a secondary source. Monitoring tropical cyclone forecasts from late June onwards matters; the South China Sea typhoon season peaks in August but can produce early systems that suppress temperatures through cloud cover and precipitation.

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

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'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.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

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.