Lowest temperature in Hong Kong on August 9?

Platform comparison

Market context

Hong Kong’s overnight low on 9 August will be set by the Hong Kong Observatory’s final “Absolute Daily Min (deg. C)” for that date, so the market is really a bet on the minimum temperature printed in the completed daily extract rather than an intraday reading. In practical terms, a programmatic trader would treat the event as a data-pull problem: monitor the Observatory’s climate pages, wait for the post-day publication of the daily extract, then map the reported minimum to the market’s temperature band. The settlement source is decimal Celsius, so a 0.1°C print can matter at the band edges.

The 0% crowd-implied price is consistent with the fact that Hong Kong in early August is normally very warm, with the Observatory’s 1991–2020 daily normal for 9 August showing a mean minimum of 26.9°C and a mean of 29.0°C. Recent weather histories also show lows staying in the high 20s Celsius: one source recorded 26.5°C on 7 August 2026, while broader historical August datasets put average lows around 25.7°C to 27°C. That makes very low bands structurally unlikely unless a strong rain band or cooler maritime air materially changes the overnight profile.

For traders using tooling, the main catalysts are the Observatory’s forecast updates, the timing of the daily extract publication, and any tropical-weather developments affecting Hong Kong’s nocturnal temperatures. The 9-day forecast dataset and current-weather pages are useful for modelling the path into the close, but settlement will depend on the final archived reading, not the forecast. Around this point in the season, markets usually react less to daytime heat than to whether cloud cover, showers, or a passing disturbance suppresses the overnight minimum.

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

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

FAQ

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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Kalshi Fees trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.

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.