Lowest temperature in Hong Kong on July 31?

Platform comparison

Market context

Hong Kong’s lowest temperature on 31 July will be set by the Hong Kong Observatory’s final “Absolute Daily Min” reading, and the current crowd-implied 2% YES price suggests traders think an unusually cool outcome is still a long shot. For a July date in Hong Kong, that is consistent with the city’s normal late-summer baseline: average July lows are around 27–28°C, with daily minima commonly staying in the high 20s rather than falling into the mid-20s. The market therefore sits well below the climatological norm, so any YES case will likely need a marked weather disruption rather than a routine overnight dip.[1][2]

Historical comparables show why the market is priced as a tail event. Hong Kong Observatory material for July highlights minimum temperatures clustered around 27.3–27.7°C in the month’s ranked records, while 31 July 2019 stands out as a rare exception when heavy rain and tropical-storm influences pulled the Observatory minimum down to 24.5°C, the month’s lowest reading.[1][3] That kind of outcome is the relevant analogue: not a seasonal average, but a sharp, rain-driven break from the usual humid pattern. The gap between the 2% market price and the broad weather norm implies only a modest probability of a similar disturbance, though not a zero one.[1][3]

Traders should watch the Observatory’s hourly readings and whether any late-season tropical system or rainband affects the city before the settlement cutoff, because the final value is taken from the published daily extract and will not resolve until that record is finalised.[6][13] At this stage there is no obvious sportsbook-style line to anchor against, so the most meaningful comparison is between the thin YES bid, the much higher no-side probability implied by July climate history, and the possibility of a storm-related downdraft that can still move the realised minimum several degrees in a single day.[3][13]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

Resolution & payout

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

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 Kalshi vs Polymarket. 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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Kalshi vs Polymarket trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.