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 temperature range containing that daily maximum. Programmatic traders should script a listener for the Observatory’s “Daily Extract” CSV feed, parsing the “Absolute Daily Max” field once the 12:00 UTC settlement window closes. The current 0% YES crowd-implied probability suggests the crowd expects the peak to fall outside the defined range, likely anticipating a standard mid-summer high rather than an extreme outlier.

Historical July maxima in Hong Kong typically cluster between 31°C and 34°C, with absolute records rarely exceeding 36°C even during intense heatwaves. The 0% probability aligns with this baseline, as no recent climatic anomaly suggests a deviation into the upper extremes required for a YES resolution. Traders building conditional orders should reference the open-data API endpoint for daily maximums to validate historical distributions before deploying automated strategies.

Key catalysts include the official publication schedule of the Daily Extract, which usually finalises data within 24 hours of the observation date. Traders must monitor the Observatory’s data portal for any delays in the CSV release, as settlement is impossible until the “Absolute Daily Max” is finalized. Recent weather reports confirm active monitoring of current conditions, but no specific announcements regarding unprecedented heat have been issued for this date yet [1]. Dependence on the CSV format means any API downtime could temporarily stall algorithmic resolution checks.

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

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is Kalshi Fees. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

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 Kalshi Fees 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.