Highest temperature in Hong Kong on July 4?

Platform comparison

Market context

On 4 July 2026, Hong Kong will face its peak summer heat as the Hong Kong Observatory records the absolute daily maximum temperature in degrees Celsius, a figure that will determine the outcome of a prediction market currently implying a 0% chance of any temperature exceeding the highest bracket. The crowd is betting heavily on the underdog, treating extreme heat as an impossibility, yet historical data suggests this contrarian stance ignores a clear pattern of record-breaking July temperatures in recent years.

July in Hong Kong has consistently delivered exceptionally high temperatures, with the city experiencing its hottest month on record in 2024, when the daily mean temperature reached 30.8°C and the maximum hit 39°C in Sheung Shui [4][5]. Even in 2021, the monthly mean maximum was 32.6°C, and in 2018, the mean maximum was 31.8°C [1][9], while the highest recorded monthly maximum since 1885 stands at 35.7°C [7]. The consensus is firmly on the favourite, assuming temperatures will stay within moderate ranges, but the value spot lies in the underdog, given the accelerating trend of heatwaves and the fact that 2026’s July has already been flagged as potentially record-breaking by the observatory [6][8].

Traders must monitor the Hong Kong Observatory’s Daily Extract for the finalized "Absolute Daily Max" figure, which is the sole resolution source and will be published only after data is confirmed [1][2]. Recent news highlights that Hong Kong has already sweltered through the hottest July day on record, with temperatures reaching 39°C, indicating that the atmospheric conditions for extreme heat are already present [5]. The key dependency is the timing of the Daily Extract publication, as the market cannot resolve until this data is officially released, making the schedule of the observatory’s updates a critical catalyst for any shift in implied probability [1][3].

Sources: 1 · 2 · 3 · 4 · 5

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 Who Will Win. 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.

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.

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.