Highest temperature in San Francisco on August 5?

Platform comparison

Market context

Polymarket has this contract spread across the low and mid-70s rather than at the extremes, with the market currently assigning 49% to both **70–71°F** and **72–73°F**, while a **0%** price on **YES** for the tail end of the distribution signals traders do not expect an unusually hot finish at San Francisco International Airport. Because settlement is based on the highest observed reading at the KSFO station on Wunderground, the trade is really about the airport’s daily peak, not the citywide headline temperature, and positions are bought with **USDC** on **Polygon** against conditional tokens that redeem only if the chosen band matches the reported high. [1][6]

The clearest historical frame is that San Francisco’s August climate is usually mild by US standards, which helps explain why the market is centred around the low-70s rather than the 80s. AccuWeather’s August page shows an average high of about **70°F** and low of **57°F**, while Weather Spark likewise puts August temperatures in a narrow summer range, so a reading in the low- to mid-70s is more consistent with climatology than a severe heat spike. [2][11] That is also why the probability mass in this contract sits close together across adjacent bands: small forecast changes around a normal August day can shift the winning bucket materially. [1][2]

A trader should watch the local forecast path into the event window, especially any Bay Area heat-wave coverage and any National Weather Service updates for the San Francisco area, because even modest marine-layer changes can push the airport’s afternoon high up or down by a degree or two. The San Francisco Chronicle reported that a broader California heat wave was expected to build from 5 August, with Bay Area temperatures likely to spike through 8 August and the NWS flagging elevated heat risk in parts of the region, which is relevant even though KSFO itself often stays cooler than inland stations. [16] On Polymarket, that means the practical question is whether late-breaking forecast revisions move the airport reading into the next bucket before Wunderground finalises the day’s history table. [6][15]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to PolyGram, which mirrors the Polymarket order book directly.

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

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%.