Highest temperature in Hong Kong on July 21?

Platform comparison

Market context

The market tracks the peak Celsius reading recorded by the Hong Kong Observatory on 21 July 2026, resolving to the specific range containing that absolute daily maximum. With the settlement window closing at noon UTC on the event date, the 0% crowd-implied probability for the current leading outcome suggests the market expects a temperature outside the offered bracket, likely indicating a consensus that the heat will be either significantly lower or higher than the specific range in play.

Historical data for mid-July in Hong Kong typically sees maximum temperatures hovering between 31°C and 34°C, though extreme heatwaves have pushed readings above 35°C in recent years. The current seasonal forecast for July–September 2026 indicates temperatures are expected to be normal to above-normal, influenced by the latest ENSO status and climate model guidance [2]. This above-normal projection frames the 0% probability as a potential mispricing if the bracket excludes the upper end of the expected range, as power-users should programmatically backtest historical July 21 extremes against the current forecast to identify arbitrage opportunities.

Traders must monitor the Hong Kong Observatory’s "Daily Extract" publication schedule, as the market cannot resolve until the "Absolute Daily Max" data is finalized and published [1]. The primary catalyst is the official release of this dataset, which will confirm the exact temperature to one decimal place. Automated bots should be configured to poll the observatory’s climate data page immediately upon the expected release time, as any delay in the "Daily Extract" could impact execution speed for conditional orders or copy-trading strategies relying on real-time settlement triggers.

Sources: 1 · 2

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

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?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

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 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.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.