Highest temperature in Guangzhou on August 17?

Platform comparison

Market context

Guangzhou's August weather pattern is entering its most consistently hot phase, with daytime highs typically ranging between 32–35°C during mid-month. The 0% implied probability suggests the market is pricing in a specific temperature threshold as effectively impossible, though without visibility on the exact range boundaries, traders are working with limited information about what constitutes the settlement outcome.

Historical August data for Guangzhou Baiyun International Airport shows extreme temperatures are rare but not unprecedented. The station has recorded readings exceeding 37°C during August heatwaves, most notably in 2013 and 2017, though such peaks typically occur in early-to-mid August rather than mid-month. The current 0% probability may reflect either an unusually high threshold or market consensus that August 17 falls outside typical peak-heat windows for the region.

The critical variable for traders is the specific temperature range embedded in the market's resolution criteria, which determines whether ordinary August conditions resolve as YES or NO. Monitoring China Meteorological Administration forecasts in the week preceding August 17 will clarify whether any unusual heat systems are developing. The resolution source—Weather Underground's Daily Observations table at Baiyun station—is well-documented and reliable, though traders should verify the exact temperature bands offered before committing positions, as the gap between historical norms and the settlement threshold appears to be driving the current pricing.

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.

UK Frequently Asked Questions

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.

Is Polymarket legal in the UK?

Polymarket is accessible to UK traders but is not UKGC-licensed. It operates under US CFTC jurisdiction. UK residents face no domestic legal prohibition on using it, but UKGC consumer protections do not apply. For UKGC-regulated alternatives, Betfair Exchange and Smarkets offer similar prediction-style markets.

Do I pay tax on prediction market profits in the UK?

UKGC-licensed platform profits (Betfair, Smarkets) are typically tax-free gambling winnings for UK individuals. Polymarket profits involve USDC crypto transactions, which HMRC treats as Capital Gains Tax events. Keep full transaction records and report via Self Assessment if gains exceed £3,000 per tax year.

How do I deposit on Polymarket from the UK?

UK traders typically fund Polymarket via Coinbase UK, Kraken or Revolut — buying USDC with GBP and transferring to a Polygon-compatible wallet (MetaMask, Coinbase Wallet). Polymarket's onboarding walks you through the bridging process. Typical GBP-to-USDC conversion costs 0.5–1%.