Highest temperature in Hong Kong on May 21?

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Market context

Hong Kong’s top temperature on 21 May will be taken from the Hong Kong Observatory’s final daily extract, using the day’s “Absolute Daily Max” in degrees Celsius. With the settlement window closing at noon UTC, the market is effectively waiting on a single official reading rather than a broader daily average, and the contract cannot resolve until the Observatory finalises the data for that date.

May is already a warm month in Hong Kong, with typical highs around 29–32C and lows in the low-to-mid 20sC, but the distribution still leaves room for a wide range on any given day. Recent years have shown that late-spring heat can spike materially: the Observatory said May 2025 reached 33.0C at its peak, while Hong Kong’s 2025 weather was broadly hotter than normal and produced many hot days and hot nights. That history suggests the relevant question is not whether it will be warm, but whether the day’s maximum lands in an ordinary May band or at an elevated threshold.

For traders, the key catalyst is the Observatory’s publication timing rather than any on-chain event. The market settles in USDC, so broader crypto conditions matter mainly through liquidity and positioning, not the weather outcome itself; BTC and ETH spot swings can still affect appetite for small-cap prediction-market risk. The main dependency is the final HKO daily extract, which can lag the observed weather and should be treated as the only source of truth for settlement. If the extract is delayed or revised, the contract remains open until the official figure is posted.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reads Highest temperature in Hong Kong on May 21? on-chain. Polymarket's quote comes directly from the Polygon order book — the only comparable venue with on-chain settlement. Kalshi (USD, off-chain), Betfair (GBP/EUR, off-chain) and Manifold (play-money) are listed for comparison. Every CTA routes to PolyGram, which mirrors the Polymarket order book directly.

Resolution & payout

Settlement is on-chain via UMA Optimistic Oracle. A proposer posts the outcome with a bond, a two-hour dispute window opens, then the smart contract lifts winning conditional tokens to 1 USDC and sends payments to holders' wallets automatically. No withdrawal fees beyond Polygon gas.

Off-chain venues (Kalshi, Betfair, Smarkets) settle in local fiat through bank-side clearing — faster than SWIFT, slower than on-chain. Manifold pays no real cash.

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.

Do I need to KYC for this market?

Not under $1,500 of lifetime trading volume. Above that threshold, PolyGram triggers a quick verification flow that finishes in minutes.