Highest temperature in San Francisco on August 5?

Platform comparison

Market context

Polymarket is pricing the San Francisco International Airport high for 5 August at **0% YES** on the named contract, even though the live distribution still implies a very wide spread across temperature bands rather than a settled outcome. On Polymarket, traders are holding conditional tokens funded in USDC on Polygon, so the market price is simply the crowd’s view of which Fahrenheit band will match the official Weather Underground reading for KSFO once the day is fully complete. [2][12]

For context, San Francisco’s August climate usually sits in a mild coastal range, with monthly normals around the upper 60s to low 70s Fahrenheit rather than the 80s and 90s seen inland. That matters because this market resolves to the *highest* temperature at the airport station, so a brief midday warm-up can shift the answer even if the day finishes cooler; the current Polymarket board already shows the main cluster around 70–73°F, with adjacent bands still close enough to reflect uncertainty rather than consensus. [1][2]

The main catalysts are the local marine layer, sea-breeze strength, and any inland heat push that spills toward the coast. Recent Bay Area coverage pointed to warmer inland conditions and only a weak sea breeze around the region, while San Francisco itself was still expected to stay much milder than the interior, which is the key dependency for a KSFO high. Traders also need to watch the Weather Underground history page itself, because the market resolves off that station’s completed daily summary rather than a generic city forecast, and the contract only settles once subsequent-day observations confirm the full day’s data are in. [19][12]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in San Francisco on August 5? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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.

UK Frequently Asked Questions

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 Polymarket Alternative UK. 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.

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%.