Highest temperature in Hong Kong on August 21?

Platform comparison

Market context

Hong Kong's daily maximum temperature on 21 August 2026 will be recorded by the Observatory's official weather station and published in their Daily Extract dataset. The settlement hinges on a single data point—the absolute daily maximum in degrees Celsius to one decimal place—making this a straightforward factual resolution once the date passes and the Observatory publishes its records, typically within days of the observation period.

August sits at the tail end of Hong Kong's summer monsoon season, when daily highs routinely exceed 32°C. Historical data from the Observatory shows August averages around 32.5°C for daily maxima, with extremes ranging from 29°C to 36°C depending on typhoon activity and atmospheric pressure systems. The 0% crowd probability suggests either extreme confidence in a specific temperature band or insufficient liquidity across the full range of options. Reviewing comparable August dates from prior years—particularly 2015 (33.7°C), 2019 (34.1°C), and 2023 (33.2°C)—establishes the typical distribution traders should expect.

For programmatic approaches, the key dependency is the Observatory's publication schedule. Traders building conditional order logic should monitor the Hong Kong Observatory's daily weather bulletins and their climate data portal; tropical storm warnings or unusual pressure anomalies in mid-August could shift expectations. The settlement window closes at 12:00 UTC on 21 August, but actual data availability typically lags by 24–48 hours, requiring integration with the Observatory's automated data feeds rather than real-time market signals.

Methodology

We track Highest temperature in Hong Kong on August 21? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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.

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