Highest temperature in Guangzhou on August 10?

Platform comparison

Market context

Polymarket has this Guangzhou temperature contract pricing a **0%** chance of the top Celsius band clearing, even though the event is still open on-chain and will settle in USDC through Polygon conditional tokens. For traders, that means the market is treating the day’s peak at Guangzhou Baiyun International Airport as effectively non-competitive against the listed threshold ranges, with the resolution ultimately tied to Weather Underground’s *Daily Observations* table rather than the summary high shown elsewhere.

That scepticism is easier to understand when set against the broader August climate in Guangzhou. Seasonal guides consistently describe August as hot, humid and rain-prone, with typical daytime highs clustered around the low-to-mid 30s Celsius and occasional peaks nearer 36°C[1][7][10][12][15][16][18]. Live forecast services this morning also point to a very warm day, with highs around 36–38°C and the hottest part of the afternoon expected after noon local time[2][3][4][6][7][8]. In other words, the market is not pricing a cool day; it is pricing the chance that the airport’s recorded maximum lands below the higher settlement buckets.

The main catalysts are mundane but decisive: the afternoon heat cycle, any rain or thunderstorm development that caps the maximum, and whether the airport station reports a brief spike before conditions ease. Because settlement depends on the station’s logged observations up to the window close, traders are watching intraday updates rather than the headline forecast alone[3][4][5]. A recent operational detail to keep in view is that Weather Underground’s station page was updating around 08:00 CST with a forecast note that temperatures should be cooler than yesterday, which matters only insofar as it may shape the day’s realised max[5].

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.

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