Highest temperature in Hong Kong on July 4?

Platform comparison

Market context

The underlying event is the peak daytime heat recorded by the Hong Kong Observatory on 4 July 2026, with official forecasts pointing to highs between 27°C and 32°C under partly cloudy skies [1]. Current crowd-implied probability sits at 0% for a "YES" outcome, suggesting the market believes the temperature will fall outside the specific range being bet on, yet Polymarket data shows 31°C as the frontrunner at 59% and 30°C at 32% [1]. This divergence marks the consensus as heavily favouring the upper end of the forecast band, while the 0% implied probability on the current market likely represents a contrarian angle where traders are pricing in a sudden drop or cloud cover that keeps temperatures below the threshold.

Historically, July in Hong Kong has seen mean maximum temperatures reach 31.8°C in 2018, with the highest monthly maximum recorded at 35.7°C between 1885 and 2019 [4][6]. The city also broke 20 weather records in 2025, with the annual mean temperature 0.8°C above the 1991 baseline, indicating a warming trend that supports the favourite of 31°C [7]. Value spots may sit on the underdog of 30°C if the scattered showers mentioned in recent forecasts materialise more heavily than anticipated, as AccuWeather predicts daily highs ranging from 86°F to 96°F (30°C to 35.5°C) for July 2026 [9].

Traders should watch the Hong Kong Observatory’s "Daily Extract" for finalised data, as the market cannot resolve until this official publication is available [4]. Recent forecasts from the Observatory indicate scattered showers and partly cloudy skies for 3–4 July, which could act as the catalyst for a contrarian drop in temperature [1]. The key dependency is the timing of the "Absolute Daily Max" release, and any delay or revision in the forecast due to sudden cloud development could shift value from the 31°C favourite to the 30°C underdog.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in Hong Kong on July 4? 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

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 Who Will Win 2026. 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'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.