Highest temperature in San Francisco on June 30?

Platform comparison

Market context

The real-world event centres on the highest temperature recorded at San Francisco International Airport on 30 June 2026, with the market resolving to the Fahrenheit range containing that peak. Current crowd-implied probability sits at 0% for any outcome above the lowest bracket, suggesting traders believe conditions will remain cool. This aligns with recent data showing the highest temperature in the preceding fortnight was just 72.6°F, while the average daily high in late June typically reaches 70°F[1][2].

Historical records reveal that San Francisco has experienced extreme heat, including 103°F on 13 June 2000 and 92°F in March 2026, yet such spikes are rare anomalies rather than seasonal norms[4][5]. The 0% implied probability reflects a divergence from sportsbook lines that occasionally offer odds on moderate heat events, whereas prediction markets here show near-total consensus on cool outcomes. Analyst consensus similarly frames June as a mild month, with lows rarely falling below 51°F and highs seldom exceeding 59°F on average days[1].

Traders should monitor the National Weather Service observations for KSFO, as any sudden shift in wind patterns or marine layer breakdown could trigger unexpected warming[3]. Recent news from the Bay Area highlights that record highs are often tied to specific atmospheric dependencies, such as the absence of the typical Pacific fog[5]. With the settlement window ending 12:00 UTC on 30 June, the focus remains on whether the marine layer persists, a factor that has consistently kept temperatures below 75°F in recent years[2].

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

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 Best Prediction Markets. 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.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.