Highest temperature in San Francisco on June 30?

Platform comparison

Market context

The underlying real-world event is whether San Francisco International Airport will record a temperature above 65°F on 30 June 2026, a threshold the market currently prices at 0% probability for a “yes” outcome. On Polymarket, this contract trades with USDC on the Polygon network, where conditional tokens reflect the crowd’s near-total certainty that the day will remain cool, likely hugging the average June high of 65–67°F[2]. The on-chain mechanics lock in liquidity now, with settlement deferred until 12:00 UTC on 30 June 2026, when Wunderground data will resolve the final temperature range[1].

Historically, June in San Francisco is rarely hot; the highest recorded temperature for the month was 103°F on 14 June 2000, an extreme outlier that broke the prior record of 103°F on 13 June 2000[6][8]. Yet typical June days stay mild, with daily highs averaging 70°F only on 29 June, and overnight lows rarely dipping below 51°F[3]. The current 0% probability aligns with this pattern: recent forecasts show Thursday’s heat wave (22 June 2026) peaking in inland valleys, while downtown San Francisco stays in the low-to-mid-80s, far from triple-digit extremes[1].

Traders should monitor the marine layer’s strength and any sudden shifts in the Pacific high-pressure system, as a weaker marine layer could push coastal temperatures higher. The SF Chronicle notes that a weaker marine layer on Thursday allowed Pacifica and Half Moon Bay to warm to 80°F, hinting at volatility if similar conditions persist[1]. Watch the National Weather Service’s daily Bay Area updates and Wunderground’s hourly KSFO data, as these are the definitive sources for resolution. No major announcements are scheduled, but the timing of the heat wave’s tail end relative to 30 June will be the critical catalyst.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in San Francisco on June 30? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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.

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 Polymarket Scam?. 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.

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.