Highest temperature in Hong Kong on June 29?

Platform comparison

Market context

The underlying real-world event is the highest temperature recorded by the Hong Kong Observatory on 29 June 2026, measured in degrees Celsius. Polymarket prices this contract today at 0% YES, implying the crowd believes the temperature will fall outside the specific range offered, despite seasonal forecasts predicting above-normal temperatures for June through August 2026[1]. Historical data frames this probability sharply; Hong Kong recently recorded its hottest day of the year so far at 34.6°C, with New Territories expected to hit 37°C during extreme heat warnings just days prior[2][5]. February 2026 was exceptionally warm, reaching 26.9°C, and the 2026 outlook projects temperatures 1.3 to 1.9 degrees above the 1850–1900 average, suggesting a high likelihood of record-breaking heat[6][8].

Traders must watch the Hong Kong Observatory’s daily extract for the finalized "Absolute Daily Max" once published, as the market cannot resolve until this data is official[1]. The immediate catalyst is the seasonal forecast confirming abnormally high temperatures for 2026, following the hottest winter residents have seen[4]. Recent news from the South China Morning Post highlights the sweltering conditions and hail warnings accompanying the 34.6°C peak, indicating that extreme heat events are already active and escalating[5]. On-chain mechanics involve USDC settlement on the Polygon network using conditional tokens, meaning liquidity will shift only when the Daily Extract confirms the specific temperature value. The dependency remains strictly on the Observatory’s finalised climate data, not real-time weather apps.

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 Polymarket Scam?. 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.

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.