Highest temperature in San Francisco on August 5?

Platform comparison

Market context

Polymarket has **0%** priced into YES for this San Francisco temperature contract, so the market is treating a qualifying high at KSFO as effectively off the board and assigning almost all value to the alternative ranges. On Polymarket, that view is expressed with USDC-backed trades on Polygon through conditional tokens, so the live price is simply the crowd’s current read on which temperature band the Wunderground KSFO history page will show as the day’s top reading.[2][13]

That pricing sits against a city that usually has a narrow August temperature profile, with AccuWeather’s August page showing San Francisco’s typical highs in the low 70s and lows in the upper 50s, while the current market leaderboard has the 72-73°F bucket at 51% and 74-75°F at 21%.[1][2] In practice, that means traders are leaning towards a modestly warm airport reading rather than a breakout heat event, which is consistent with the way coastal San Francisco often differs from inland Bay Area locations. The relevant reference point is the San Francisco International Airport Station, not the citywide average, and the outcome is settled off the Wunderground daily-history display for that station.[13]

For catalysts, the main driver is the short-range forecast into the afternoon peak at KSFO: any shift in marine layer depth, sea breeze strength or cloud cover can move the final bucket by a degree or two, which matters because these contracts resolve in ranges. The local forecast context around 5 August pointed to mostly clear conditions and warm inland air, while regional coverage noted San Francisco was expected to stay in the 70s and 80s unless the sea breeze weakened more than expected.[17][18] Because the market closes on the Wunderground history record, a trader is really watching the day’s observed airport temperature progression, not the city’s headline forecast alone.[13]

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

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

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.

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.

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%.