Highest temperature in Hong Kong on July 31?

Platform comparison

Market context

Hong Kong’s highest temperature on 31 July will be set by the Hong Kong Observatory’s daily maximum at the observatory station, reported later in the final Daily Extract in degrees Celsius to one decimal place. At 2 p.m. HKT today the Observatory was already at 31°C, with several urban and outlying sites at 31–33°C, so the market is essentially a question of whether the afternoon peak edges above the low-30s or remains contained by cloud, showers, or onshore flow.[5]

For calibration, July in Hong Kong is normally hot and humid, but the upper tail is what matters for this market. The Observatory’s July ranking shows the monthly absolute maximum record is 35.7°C, with 35.6°C in 2016 and 35.4°C in 2005, while 2023 produced 36.1°C on 27 July, illustrating that late-month extremes can still occur when heat builds under favourable summer conditions.[2][8] A crowd price of 0% YES implies the market is treating a very high reading as unlikely, but programmatically that is best read as a probability on the exact final band, not on whether it gets “hot”.[2][8]

The main catalysts are the Observatory’s hourly bulletins through the afternoon, any thunderstorm or rain bands affecting southern China and the Pearl River estuary, and the timing of the final daily extract once the day is closed. A bot or conditional-order workflow would typically watch the live Observatory feed, map the running maximum into the market’s settlement bands, and only update conviction after the official daily summary is published, since this market cannot resolve until that data is finalised.[5][11]

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 Bot 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.

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