Highest temperature in Hong Kong on June 30?

Platform comparison

Market context

The real-world event hinges on the Hong Kong Observatory’s recorded maximum temperature for 30 June 2026, specifically whether it stays within the range implied by the current 96% YES probability. This single data point, published in the Observatory’s “Daily Extract” as the “Absolute Daily Max (deg. C),” will determine the market’s resolution once finalized.

Historically, Hong Kong’s June daily maxima cluster between 29°C and 34°C, with the highest monthly mean maximum for June reaching 32.4°C in 2016[8]. Recent records show extreme heat, including a peak of 35.6°C earlier this year[9], yet the Observatory has warned that such scorching conditions are rapidly giving way to severe weather, including nine consecutive days of rain expected to start this weekend[2]. For a power-user evaluating this market programmatically, the key is to monitor the shift from heat to wet weather, as the incoming trough of low pressure will likely cap temperatures in the 26–30°C range[2], making the current high probability of a lower range outcome statistically sound.

Traders should watch the Hong Kong Observatory’s official weather bulletins for updates on the low-pressure trough and thunderstorm activity, which are expected to peak on Sunday and Monday[2]. The primary dependency is the finalisation of the “Daily Extract” data for 30 June, which will only be published after the date concludes. A recent report from The Standard confirms that relief from the heat is imminent due to prolonged wet weather, suggesting that any automated trading bot should factor in this cooling trend when assessing the likelihood of temperatures exceeding the implied range[2]. The settlement window closes at 12:00 UTC on 30 June 2026, leaving no room for late data revisions.

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

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

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.

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.

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 Kalshi Fees trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.