Highest temperature in Hong Kong on May 31?

Platform comparison

Active sub-markets

Market context

On 31 May 2026, the Hong Kong Observatory will record the day's maximum temperature in degrees Celsius. This market settles on that single daily reading, published in the Observatory's Daily Extract climate data. The settlement window closes at 12:00 UTC on that date, though resolution cannot occur until the Observatory publishes its finalised figures—typically within 24–48 hours of the observation day. Traders on Polymarket, Kalshi, Betfair and Smarkets will see this event priced differently: Polymarket displays implied probability directly; Kalshi and Betfair use decimal odds; Smarkets similarly uses decimal format. Fee structures vary materially—Kalshi charges a flat 2% on net winnings, whilst Betfair's commission scales from 2% to 5% depending on market liquidity. Polymarket's fee sits at 2% on winnings. Geographic reach differs too: Kalshi operates under CFTC oversight and restricts US-based traders; Betfair and Smarkets operate under UK gambling licences; Polymarket's regulatory status remains contested in several jurisdictions.

Hong Kong's May temperatures are climatically stable. Historical data from the Observatory shows late May daily maxima typically range between 28°C and 32°C, with extremes rarely exceeding 33°C. The 0% crowd probability on Polymarket suggests traders are pricing in no realistic scenario for the market's lowest temperature band, indicating confidence in a mid-to-high May reading. The absence of meaningful liquidity or trading activity on alternative platforms for this specific date underscores how niche weather markets fragment across venues.

Methodology

We read Highest temperature in Hong Kong on May 31? from four platform perspectives: Polymarket (on-chain CLOB), Kalshi (CFTC-regulated exchange), Betfair Exchange (sports book exchange), Smarkets (peer-to-peer betting exchange). Polymarket's live quote comes directly from the Polygon order book; the other three are listed with their platform attributes — fees, KYC, settlement currency, payment options — because a 1:1 contract comparison without API access would be guesswork.

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

Is this market available outside the US?

Polymarket Alternative 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 Polymarket Alternative UK?

Zero. Polymarket Alternative UK 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.

Do I need to KYC for this market?

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