Highest temperature in Hong Kong on July 20?

Platform comparison

Market context

The market tracks the peak Celsius reading recorded by the Hong Kong Observatory on 20 July 2026, resolving only once the official “Absolute Daily Max” appears in the finalized Daily Extract. With the crowd-implied probability at 0% for a YES outcome, the current pricing suggests the market expects the temperature to fall outside the specific range defined by the contract, likely due to the extreme heat typically associated with mid-summer in the region.

Historical data shows Hong Kong frequently experiences highs exceeding 33°C in July, with the Observatory’s records indicating consistent summer peaks that often breach 34°C [1]. A 0% probability is statistically anomalous for a mid-summer date unless the contract range is set well below the historical median, such as below 30°C, which would be a rare deviation from the norm. Traders should treat this as a potential mispricing if the range aligns with typical July extremes, as comparable years show no sustained cooling to such lows during this period [2].

Programmatic approaches to this market require monitoring the Hong Kong Observatory’s open data API for the CLMMAXT endpoint, which publishes the daily maximum in CSV format [1]. The primary catalyst is the release schedule of the Daily Extract, which typically finalizes data shortly after midnight local time, creating a hard dependency for settlement. No external weather announcements alter the resolution, as the Observatory’s finalized figure is the sole determinant; automated bots should poll the API every 15 minutes post-settlement window start to capture the value before manual verification.

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

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

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 Polymarket Review UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

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.

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.