Highest temperature in Hong Kong on July 21?

Platform comparison

Market context

Hong Kong is bracing for a sharp heat spike as an anticyclone aloft clears skies over the Guangdong coast, pushing Tuesday’s forecast high to approximately 33°C after Monday’s record 32°C[2]. This immediate intensification contradicts the market’s 0% YES probability for any temperature range below 33°C, suggesting traders may be underestimating the persistence of the current “very hot” spell expected to last another day or two[2].

Historical July data frames this outlier risk: while average highs sit near 29°C (89°F), the city has frequently breached 32°C during El Niño years, with the 2026 seasonal forecast warning of normal-to-above-normal temperatures as strong El Niño conditions develop late summer[3][7]. The 0% pricing ignores that even a brief lull in cloud cover could push the Observatory’s “Absolute Daily Max” into the 33–34°C bracket, a range seen in comparable anticyclone-driven heatwaves in recent decades.

Traders must monitor the Hong Kong Observatory’s 9-day forecast updates for shifts in thunderstorm timing, which could suppress the peak if showers intensify before afternoon[1]. The key catalyst is the finalisation of Tuesday’s “Daily Extract” data, expected within hours of the 12:00Z settlement window, as any delay in publishing the “Absolute Daily Max” will prevent resolution[2]. Watch for official confirmations of the heat persisting through Wednesday, as forecasters note the “very hot” conditions are likely to hold before scattered showers arrive later in the week[2].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in Hong Kong on July 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

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

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 Prediction Today. 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'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.

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.