Highest temperature in Hong Kong on August 4?

Platform comparison

Market context

Polymarket currently prices this Hong Kong heat contract with **30°C** leading at **40%** and **29°C** close behind at **34%**, which tells you traders are clustering around a fairly narrow late-summer range rather than pricing a runaway heat extreme.[2] On Polymarket, that view is expressed in USDC on Polygon through conditional tokens, so each cent of price is simply the crowd’s live implied probability for the day’s final HKO maximum, not a forecast of any single station reading.[2][3]

That pricing sits broadly in line with Hong Kong’s August climatology, where highs are typically in the upper 20s to low 30s Celsius, but it leaves room for warmer outcomes if a hot air mass, strong sunshine, or weakened rain cover pushes the daily maximum up during the afternoon.[1][7][10] Recent local reporting also shows how quickly readings can spike in summer: Hong Kong has already logged a hottest day of 2026 with temperatures above 34°C in parts of the territory, reminding traders that the upper tail remains live even when the modal outcomes sit near 30°C.[9][11]

For resolution, the key watchpoint is the Hong Kong Observatory’s published “Daily Extract” for 4 August, because the market settles only once the HKO finalises the “Absolute Daily Max (deg. C)” for that date.[3][13] Traders should also watch the Observatory’s regional weather updates and any typhoon or heavy-rain signals, since cloud cover and rainfall can cap the daytime maximum and shift the odds between adjacent temperature buckets before the market closes.[6][17]

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

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

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 PolyGram. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

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 Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

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.