Highest temperature in Hong Kong on July 21?

Platform comparison

Market context

The market tracks the peak Celsius reading recorded by the Hong Kong Observatory on 21 July 2026, resolving to the specific temperature range containing that daily maximum. Power-users approaching this programmatically will query the Observatory’s open data API for the “Absolute Daily Max” field once the relevant Daily Extract is finalized, bypassing manual checks for automated settlement triggers.

Historical July peaks in Hong Kong typically range between 33°C and 36°C, with the absolute record for the month reaching 36.4°C in 2017. The current 0% crowd-implied probability for any specific outcome suggests the market lacks sufficient liquidity or data to price a range, rather than indicating an impossible event; traders should treat this as a null state awaiting volume rather than a definitive bearish signal on high temperatures.

Key catalysts include the publication schedule of the Daily Extract, which usually follows the observation date by one to two days, and any extreme heat announcements from the Observatory that might correlate with record-breaking conditions. Traders monitoring the API endpoint at data.weather.gov.hk must verify the CSV feed for the CLMMAXT dataset to confirm data availability before executing conditional orders, as settlement cannot occur until the official figure is published [2]. Recent climate reports highlight increasing summer heat intensity in the region, reinforcing the likelihood of temperatures exceeding 34°C during this period.

Sources: 1 · 2

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 Review 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.

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 Review UK 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.