Highest temperature in Hong Kong on August 2?

Platform comparison

Market context

Hong Kong’s afternoon peak on 2 August will be set by the Hong Kong Observatory’s **Absolute Daily Max** for that date, recorded to one decimal place and only final once the daily extract is published. That means the market is not about a forecast high, but about the highest observed temperature in the official record, so a programmatic approach should anchor on the Observatory dataset rather than model output or app-level weather feeds. [13][3]

The current 0% YES probability is hard to reconcile with Hong Kong’s August climatology, which usually sits in the high 20s to low 30s Celsius. The Observatory’s normal for 2 August shows a mean maximum of 31.5°C, while other climate summaries put August highs around 29–31°C, and a recent Polymarket page on the same event had 27°C and 28°C as the leading outcomes, suggesting the crowd was clustering around a much cooler-than-average day even before final data arrives. [6][1][8]

For traders using bots, copy-trading or conditional orders, the key catalyst is the timing of the Observatory’s publication, because this market cannot settle until the relevant Daily Extract is posted. The market rules also say later revisions to already published temperatures for the timeframe will not count, so the practical trigger is the first finalised release, not any retrospective correction. Forecasts on the Observatory site around the event called for heavy showers, thunderstorms and a 24–28°C range, which would favour a low ceiling unless a brief break in cloud cover produces an outlier spike. [1][13][3]

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 Kalshi Fees. 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.

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.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.