Highest temperature in Hong Kong on July 21?

Platform comparison

Market context

On 21 July 2026, the Hong Kong Observatory will record the day's maximum temperature in degrees Celsius. That reading, published to one decimal place in the Observatory's Daily Extract, will determine which temperature band this contract resolves to. The crowd currently prices all outcome ranges at 0% YES, reflecting the standard state of markets for future weather events where no single outcome has yet crystallised into tradeable conviction. Settlement occurs at 12:00 UTC on that date, though the actual Observatory data may take several hours to finalise and publish.

Hong Kong's July temperatures exhibit narrow historical variance. The Observatory's records show July daily maxima typically cluster between 32°C and 34°C, with extreme readings rare. The all-time July maximum stands at 36.3°C (recorded in 1975), whilst readings below 30°C occur in fewer than 5% of cases. This tight distribution means most outcome ranges in this market will remain improbable until atmospheric conditions in mid-2026 become observable. Comparable July days from recent decades—2015, 2019, 2022—saw maxima between 32.5°C and 33.8°C, establishing a baseline against which unusual heat or cooler patterns would register.

Traders monitoring this contract should track seasonal weather forecasts from April 2026 onwards, particularly signals of El Niño or La Niña phases, which influence East Asian summer temperatures. The Hong Kong Observatory publishes monthly outlooks that may shift probability distributions as July approaches. Typhoon activity in early July could suppress temperatures, whilst sustained high-pressure systems would elevate them. Real-time satellite data and regional model consensus become actionable only in the final week before settlement.

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 PolyGram. 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.