Highest temperature in Hong Kong on June 20?

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Market context

Hong Kong’s highest temperature on 20 June will be set by the Hong Kong Observatory’s “Absolute Daily Max” reading, and the market only resolves once that daily extract is published and finalised. The current crowd-implied probability of **0% YES** is strikingly low for a late-June temperature contract, because the Observatory’s own outlook for June 2026 called for **normal to above-normal** temperatures, with high temperatures expected to affect southern China early in the month.[2]

For context, June has produced genuinely hot outcomes in Hong Kong before: the Observatory reported a June 2025 maximum of **35.6°C**, which tied the June record maximum, and 2025 was marked by multiple weather records.[9][5] That matters because contracts like this can move sharply on a single heat spike, while long-run seasonal forecasts such as the Observatory’s June-August view still point to **above-normal** temperatures overall.[1] By comparison, third-party monthly outlooks have also leaned warm, with AccuWeather showing June highs around the upper 80s to low 90s Fahrenheit, which is broadly consistent with a warm regime rather than an unusually cool one.[3]

The main catalysts are the Hong Kong Observatory’s short-range heat and rain updates, plus any monsoon-driven shifts that can cap daytime maxima through cloud and showers. The Observatory’s June forecast noted that the southwest monsoon could bring unsettled weather in the second week of June, which is the sort of dependency that can depress a daily high even in a warm month.[2] In practice, the contract’s outcome will be driven less by the monthly mean than by whether 20 June itself stays sunny and humid, or turns wetter and cloudier ahead of the settlement cut-off and the final daily extract publication.[2]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in Hong Kong on June 20? on the five venues with material liquidity for prediction markets. Live odds come from the Polymarket Polygon order book — the only source that ships real-time data under an open licence. For Kalshi, Betfair and Manifold we list platform attributes (fee, KYC, settlement, payment) instead of fabricated odds, because their APIs use non-comparable contract definitions.

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?

On Best Prediction Markets UK, which mirrors the Polymarket order book at 0% fees. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

Is this market available outside the US?

Best Prediction Markets UK is available in most jurisdictions where Polymarket isn't directly accessible. Polymarket itself is geo-blocked in the US/UK/EU. Always check local regulations.

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 it cost to trade on Best Prediction Markets UK?

Zero. Best Prediction Markets UK routes every order to the live Polymarket order book; the only cost is the Polygon network fee, typically under $0.01 per transaction.

Do I need to KYC for this market?

Not under $1,500 of lifetime trading volume. Above that threshold, Best Prediction Markets UK triggers a quick verification flow that finishes in minutes.