Highest temperature in San Francisco on June 30?

Platform comparison

Market context

The real-world event at hand is the highest temperature recorded at San Francisco International Airport on 30 June 2026, with the market currently pricing a sub-66°F outcome at 0% implied probability. This starkly contrasts with historical patterns: AccuWeather forecasts June highs in San Francisco typically range between 62°F and 70°F, while climate data identifies 22 June as the warmest day on average, reaching 72.7°F [4][5]. Recent Polymarket activity for 29 June saw a 100% probability assigned to 72–73°F, suggesting traders expect similar warmth for the 30th, whereas Kalshi’s identical market on the same date shows a 0% chance for the “65°F or below” outcome, mirroring the current crowd-implied probability but using decimal odds rather than implied percentages [2][3].

Traders should monitor the National Weather Service’s daily climatological release, which will verify the maximum temperature and trigger settlement shortly after 7:00 or 8:00 AM ET on 30 June, with final trading ending at 11:59 PM local time [2]. While no specific heatwave announcement has been confirmed for 30 June, Reddit discussions indicate the Bay Area may be experiencing its fourth heatwave of 2026, with temperatures frequently exceeding 75°F since February [10]. Platform divergence remains critical: Polymarket displays outcomes like 68–69°F at 35% with no KYC, whereas Kalshi requires identity verification and offers decimal odds (e.g., 0.00 for the low outcome), and Betfair or Smarkets would apply different fee structures and liquidity models, making cross-platform arbitrage possible if implied probabilities drift [1][2].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares Highest temperature in San Francisco on June 30? specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. The live probability is the Polymarket mid; the comparison columns summarise each venue's fee structure, KYC, settlement currency and payment rails. Every CTA routes to Kalshi Alternative UK, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Polymarket settles via UMA Optimistic Oracle on Polygon. A proposer posts the outcome with a bond, the two-hour window runs, then the smart contract pays USDC.

Kalshi settles USD through the CFTC-regulated clearinghouse — the cleanest variant, with heavier KYC. Betfair Exchange settles in account currency (GBP/EUR), net of 2-5% commission. Smarkets follows the same model as Betfair with a lower default 2% commission.

FAQ

Polymarket vs Kalshi — which is better?

Depends on your location. Kalshi is CFTC-regulated, US-only with full KYC. Polymarket is global, on-chain, no KYC up to $1,500. Polymarket has ~10x higher liquidity but higher regulatory risk.

What does Polymarket cost vs Kalshi?

Polymarket: 0% fees, only Polygon network costs (~$0.01/trade). Kalshi: up to 7% per trade plus spread. For high-frequency traders, Polymarket is dramatically cheaper.

Is Betfair a Polymarket alternative?

Only partially. Betfair Exchange is UK-focused with a sports-betting emphasis; they have politics markets but with thinner liquidity than Polymarket. Settlement in GBP/EUR, 2-5% commission on winnings.

Which platform is accessible globally?

Polymarket is geo-blocked in the US/UK/EU. Kalshi is US-only. Betfair and Smarkets are UK-restricted. Kalshi Alternative UK has a different geo footprint and routes to Polymarket's order book at 0% fees.

Are all these platforms regulated?

No. Kalshi is CFTC-regulated (US). Betfair and Smarkets are UK Gambling Commission licensed. Polymarket operates without explicit regulation — a different risk profile than a regulated sportsbook.