Highest temperature in San Francisco on June 30?

Platform comparison

Market context

The underlying real-world event is the highest temperature recorded at San Francisco International Airport on 30 June 2026, measured in degrees Fahrenheit. Polymarket prices this contract today with a 0% implied probability for the "YES" outcome, suggesting the market believes the temperature will fall outside the specific range defined for a win. This near-zero pricing is stark when viewed against historical June data, where the highest daily average high temperature reaches 70°F on 29 June, and recent 2026 readings between 14 and 29 June peaked at 72.6°F[1][2]. While record highs in the Bay Area have hit 103°F in 2000 and 106°F in 2017, typical June conditions rarely exceed 75°F, making the current probability a reflection of the narrow range rather than an absence of heat potential[5].

Traders should monitor the National Weather Service observations for KSFO and any sudden shifts in the Pacific High pressure system, which dictates coastal fog and temperature inversions. A key catalyst is the upcoming heat wave forecast for the broader Bay Area, as recent reports indicate the region is experiencing its hottest week since 1939 with average daily maximums near 90°F[9]. On-chain mechanics remain central to the trade: positions are settled in USDC on the Polygon network using conditional tokens, meaning liquidity and slippage will dictate entry costs as the settlement window closes on 30 June 2026 at 12:00 UTC. The resolution source is strictly Wunderground data for the airport station, so any discrepancy between downtown and airport readings could invalidate a trade based on urban heat trends[3][8].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in San Francisco on June 30? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Kalshi UK, which mirrors the Polymarket order book at 0% fees.

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 UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

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 UK trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.