Highest temperature in Sao Paulo on August 7?

Platform comparison

Market context

Polymarket is pricing the contract at **about 100% for 25°C** and **0% for the lower bands**, so the market is treating a mild São Paulo afternoon as effectively locked in rather than a live weather bet.[1] The event settles in USDC on Polygon through conditional tokens, and the relevant figure is the **highest temperature in the Daily Observations table** for São Paulo-Guarulhos International Airport, not the headline Day High & Low summary.[1] Revisions still count until the first reading for the following date is published, which matters because the official end point is the observed maximum, not a forecast.[1]

That pricing fits the broader August pattern in São Paulo, where late-winter highs often sit in the mid-20s Celsius rather than extreme heat. Local reporting for 7 August pointed to a dry, sunny day with a high near **25°C**, while CGE’s city forecast also centred on **25°C** for the capital, with night temperatures easing into the teens.[5][9] Similar market behaviour is typical when the forecast band is narrow: the final outcome often clusters around the most likely single reading, and traders only see meaningful repricing if a forecast shifts enough to threaten a different temperature bucket.[1][11]

A trader watching this market should focus on the airport station’s published observations rather than city-wide headlines, because the settlement source is Weather Underground’s station data and small discrepancies are resolved from that table.[1] The key catalyst is the publication of the next day’s first datapoint, which can freeze the settlement-relevant record if late edits appear.[1] In practice, that means late-evening updates, station timing, and whether the airport logs a brief spike above 25°C are more important than the broader São Paulo forecast narrative.[1][9]

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

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 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.

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%.