Highest temperature in San Francisco on July 13?

Platform comparison

Market context

San Francisco is bracing for a cool, fog-drenched July 13 as a persistent moist boundary layer continues to cap daytime highs, keeping the market’s 6% YES probability for a significant heat spike well grounded in current climatology. Over the last 24 hours, ensemble guidance has reinforced a stable inversion that prevents the temperature from breaking the typical 67–71 °F range, with most models capping the day near 70–75 °F and only a few allowing modest warming if the inversion lifts earlier [1].

Historical July data frames this low probability sharply: daily highs in San Francisco rarely exceed 79 °F and typically hover around 70 °F, with fog lingering into midday acting as a natural thermostat [3]. The closely priced 72–73 °F outcome on the adjacent July 12 market reflects this norm, while the current 6% YES implies traders see almost no chance of a heat dome breaching the coastal barrier, consistent with the cooler Pacific system that has kept extreme 100s away since early July [1][6].

Traders should monitor the National Weather Service’s inversion lift forecasts and any sudden shifts in the Pacific high-pressure ridge, as these are the primary catalysts for a temperature breakout. While a record July tide is forecast for Monday at 1.7 ft above normal due to thermal expansion, this marine phenomenon does not directly drive peak air temperatures, leaving the focus on atmospheric stability rather than tidal events [4]. No major heat dome announcements have been issued for the Bay Area this week, further supporting the market’s conservative stance [10].

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.

FAQ

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.

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.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

Do I need to KYC for this market?

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