Highest temperature in Shanghai on August 9?

Platform comparison

Market context

Shanghai’s highest temperature on 9 August will be read from Weather Underground’s **Daily Observations** table for Shanghai Pudong International Airport Station, not the summary “Day High & Low” figure. That makes the practical task for a trader a data-extraction problem: the relevant number is the day’s observed peak in the station log, converted into one of the market’s settlement bands, rather than the headline forecast shown elsewhere. Forecast products for the date are already clustered around the mid-30s Celsius, with AccuWeather showing an 85°F high and Weather.com.cn showing heavy rain with a 29°C high, so the tape is pointing to a warm-but-weather-volatile day rather than an extreme outlier.[3][14]

For calibration, comparable Shanghai August climatology suggests daytime highs are usually in the low 30s Celsius, with average August highs around 31°C to 32°C and monthly ranges commonly spanning the mid-20s to low-30s.[1][16][17] That matters because a 0% implied YES price is only coherent if the market is pinned to a specific band that looks materially unlikely from the current forecast set, or if participants are discounting the chance that the station’s observed maximum lands in the targeted interval after rain, cloud, or timing effects. Programmatically, this is the kind of market where a bot would poll the Wunderground station page near and after the settlement cut-off, compare the observed maximum against the band map, and only then place or hedge orders.

The main catalysts are the actual Shanghai hourly observations, the arrival timing of rain bands, and any late forecast revisions from major weather desks. AccuWeather’s near-term forecast already calls for periods of rain, becoming heavy, with strong easterly winds and a 97% precipitation chance on 9 August, while WorldWeatherOnline likewise expects very high rain and wind and Weather.com.cn flags heavy rain.[3][12][14] For a power user running conditional orders, the useful trigger is not the forecast headline but whether early-morning warmth is enough to establish the day’s maximum before convective rain suppresses later readings; a high recorded before the main rain shield arrives would resolve differently from a cooler, rain-dominated profile.

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.

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%.