Highest temperature in Hong Kong on May 21?

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Market context

Hong Kong is already past the settlement window, so the key question is whether the Observatory’s final daily extract shows any late-morning warmth before noon or whether the day locked in earlier. On an absolute daily maximum basis, the reading usually comes from the warmest part of the afternoon, not the morning, which makes a noon cut-off especially important for final classification. Recent May conditions have been warm to hot, and the city has already seen unusually high temperatures in recent years, including a 33.0C peak in May 2025 and a generally warmer-than-normal month, according to the Hong Kong Observatory.

For context, Hong Kong’s May climate typically features highs around 29–30C and rising humidity, with late May often warmer than the start of the month. But the market is not about a monthly average; it hinges on the single highest observation recorded on 21 May. That means the relevant historical analogue is a normal spring day with a midday-to-afternoon climb, rather than the broader May climate pattern. The crowd-implied 0% YES reflects how tightly the settlement rule is defined and the fact that, once the daily extract is finalised, there is little room for reinterpretation.

Traders should watch the Hong Kong Observatory’s daily extract page, which is the settlement source, and any midday updates or late corrections to station data. The main dependency is whether the maximum temperature at the Observatory occurs before the noon UTC settlement deadline and is then confirmed in the final “Absolute Daily Max (deg. C)” entry. Recent Hong Kong weather reporting has highlighted warmer springs and elevated temperature records in 2025, but for this market the decisive factor is the specific station reading on the specified date, not the broader seasonal trend.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in Hong Kong on May 21? across five venues. We show live odds for Polymarket-based markets (sourced from the Polygon order book); for other venues we list platform attributes, since the comparable contracts are not exposed via a public API on every venue. Every CTA points at PolyGram — the application we operate, where you trade directly against the Polymarket order book at 0% fees.

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.

FAQ

Is this market available outside the US?

PolyGram is available in most jurisdictions where Polymarket isn't directly accessible. Polymarket itself is geo-blocked in the US/UK/EU. Always check local regulations.

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 it cost to trade on PolyGram?

Zero. PolyGram routes every order to the live Polymarket order book; the only cost is the Polygon network fee, typically under $0.01 per transaction.

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.