Highest temperature in Hong Kong on June 21?

Platform comparison

Active sub-markets

Market context

Hong Kong’s highest temperature for 21 June will be set by the Hong Kong Observatory’s final daily extract, not by an intraday screen, so the key question is where the day’s *maximum* ends up once the data are published. The current crowd price of 0% for YES is difficult to read as a pure weather forecast because the market wording resolves to a temperature band, and Hong Kong in June is typically in the high 20s to low 30s Celsius under the southwest monsoon, with humidity often above 80%.[1][3]

The comparison point for traders is that this market already has a plausible June distribution: Polymarket’s own pricing for the same event has 32°C as the frontrunner at 47% and 33°C next at 34%, while Hong Kong has previously matched or exceeded 34°C on the summer solstice in hot years.[1][4] The observatory also shows a long-run warming trend, with mean temperatures in Hong Kong rising over time, which matters for comparing today’s book against older seasonal intuition.[5] On Kalshi, Betfair or Smarkets, the same temperature outcome would usually be expressed as decimal odds rather than a direct implied probability, and fees, maker-taker costs and KYC access can shift the effective price even when the weather view is the same.

For catalysts, traders should watch the Hong Kong Observatory’s daily extract publication timing and any short-term forecast updates, because the market cannot settle until the final 21 June record is posted.[3][9] Any afternoon surge in sunshine or a hotter-than-expected subtropical ridge would matter most, since Hong Kong’s daily maximum is usually reached later in the day rather than near sunrise.[3][4] Platform structure also matters here: Polymarket reflects crowd-implied probability directly, while exchange-style books such as Betfair or Smarkets can show a different shade of risk because of back/lay spreads, commission, and whether a user can pass KYC and access the relevant market at all.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares Highest temperature in Hong Kong on June 21? specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. Live odds come from the Polymarket order book; the other venues' contract details are maintained manually because their APIs aren't directly comparable. Every CTA routes to Polymarket Alternative, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Polymarket settles via UMA Optimistic Oracle on Polygon. A proposer posts the outcome with a bond, the two-hour window runs, then the smart contract pays USDC.

Kalshi settles USD through the CFTC-regulated clearinghouse — the cleanest variant, with heavier KYC. Betfair Exchange settles in account currency (GBP/EUR), net of 2-5% commission. Smarkets follows the same model as Betfair with a lower default 2% commission.

FAQ

Where can I trade this market with the lowest fees?

On Polymarket Alternative, 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?

Polymarket Alternative 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 does it cost to trade on Polymarket Alternative?

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

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.