Highest temperature in San Francisco on August 13?

Platform comparison

Market context

On 13 August 2026, the highest temperature recorded at San Francisco International Airport will fall into one of several defined ranges. The market resolves using the Daily Observations table from Weather Underground rather than the Day High & Low summary—a distinction that matters when automated systems pull data. For programmatic traders, this means building a parser that targets the correct data table; mismatched sources have historically caused resolution disputes on weather markets. The settlement window closes at midday UTC, giving traders a narrow window after the observation period ends.

San Francisco's August temperatures typically range between 65–75°F, with historical highs rarely exceeding 85°F at the airport station. The 0% crowd probability suggests the market may be pricing in an unusually cool day or reflecting low trading volume rather than genuine meteorological expectation. Comparable August days from 2015–2024 show the airport station recording highs between 62–80°F; only three years saw temperatures above 78°F. A trader evaluating this market should cross-reference historical volatility patterns and consider whether the probability reflects actual weather forecasting or merely thin liquidity.

Key dependencies include the Pacific high-pressure system's position in early August and any marine layer persistence. The National Weather Service Bay Area forecast, updated daily through early August, will be the practical leading indicator. Conditional orders triggered on specific forecast thresholds—say, when the seven-day outlook shows a predicted high above 80°F—could automate entry logic. Weather Underground's data feed updates hourly; integrating live pulls into a bot would allow real-time position adjustments as the observation day approaches.

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

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.

FAQ

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 Kalshi Fees. 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.

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.

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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Kalshi Fees trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.