Highest temperature in Hong Kong on July 31?

Platform comparison

Market context

Hong Kong’s official temperature read will come from the Observatory’s **absolute daily maximum** for 31 July, and the market is effectively asking whether that top reading lands in the bucket above the present crowd view of **0% YES**. That pricing implies the market is treating a materially high result as very unlikely, despite Hong Kong’s late-July climate normally sitting in the upper 20s to low 30s Celsius and occasionally pushing higher in hot spells.[3][4][6][16]

The historical frame matters because Hong Kong has seen both routine July heat and sharp spikes: the Observatory recorded **36.1°C** on 27 July 2023, one of the month’s highest readings on record, while recent public reports also show individual summer days reaching **31.6°C** and local highs above **33°C** in the New Territories and outlying districts.[8][14][7] That makes a zero-priced contract look far more conservative than a simple seasonal average would suggest, especially if the contract’s strike bands are clustered around the low-30s rather than the high-20s.

For traders, the key catalysts are straightforward: the Observatory’s hourly readings through the afternoon, any late-day convective heating, and the eventual publication of the daily extract that finalises the official maximum.[12] Because the settlement source is the Hong Kong Observatory rather than private forecasters, sportsbook-style weather lines and prediction-market prices can diverge until the day’s peak is locked in; in practice, the decisive input is whether the Observatory’s Tsim Sha Tsui station prints a peak near or above the relevant threshold before the extract is posted.[7][12]

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 Best Prediction Markets 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.

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.