Highest temperature in Hong Kong on July 21?

Platform comparison

Market context

On 21 July 2026, the Hong Kong Observatory will record the highest daytime temperature in degrees Celsius, determining which pre-set range resolves this weather prediction market. In prediction markets, a YES share pays out if the specific outcome occurs, while a NO share pays out if it does not; traders buy these shares based on their assessment of the likelihood, with prices reflecting the crowd-implied probability. Here, the crowd currently assigns a 0% chance to the YES outcome, suggesting near-universal belief that the temperature will fall outside the specific range being wagered on, though the market remains open until the official data is published.

Historical July temperatures in Hong Kong typically range between 28°C and 34°C, with absolute daily maxima often reaching 35°C or higher during heatwaves, making a 0% probability for a specific high range unusual unless that range is exceptionally extreme or implausibly low. Comparable cases from recent years show that while extreme heat is possible, the distribution of daily maxima is well-documented, and markets often correct initial mispricings once seasonal patterns are weighed against the specific range offered. The current pricing implies the selected range is either far above the realistic maximum or below the typical minimum for this date.

Traders should monitor the Hong Kong Observatory’s scheduled release of the “Daily Extract” containing the “Absolute Daily Max (deg. C)” for 21 July, as settlement depends entirely on this finalized figure. No external news announcements will alter the outcome, but delays in data publication could postpone resolution beyond the 2026-07-21T12:00:00Z window. The primary catalyst is the official confirmation of the temperature value, which will be published on the Observatory’s climate information page once the daily data is verified and finalised[1].

Sources: 1

Methodology

This page reviews Highest temperature in Hong Kong on July 21? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Prediction Market UK, which mirrors 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

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 Prediction Market UK. 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.

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.

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.

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.