Highest temperature in San Francisco on June 30?

Platform comparison

Market context

The real-world event centres on the peak temperature recorded at San Francisco International Airport on 30 June 2026, a date historically marked by mild coastal conditions rather than extreme heat. Current crowd-implied probability sits at 0% for any temperature exceeding typical ranges, suggesting traders view a scorching day as virtually impossible given the region’s maritime climate.

Historical data frames this probability with clarity: June in San Francisco usually sees average highs near 70°F, with the highest daily average reaching 70°F on 29 June[1]. Recent records show temperatures peaking at 72.6°F between 14 and 29 June 2026[2], while all-time extremes in the Bay Area reached 103°F in 2000 and 106°F in 2017, both on dates far removed from late June[5]. The 0% implied probability aligns with these patterns, as late June rarely approaches such highs.

Traders should monitor the National Weather Service’s hourly observations for KSFO, which track real-time temperature fluctuations and heat indices[3]. A recent analysis by ABC7 News notes that record highs in the Bay Area typically occur during inland heatwaves in July or September, not June[5]. No major weather announcements are scheduled, but the absence of a Pacific marine layer could act as a catalyst; however, current forecasts suggest stable conditions, reinforcing the market’s low-risk stance.

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 PolyGram. 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 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 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.

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.