Highest temperature in San Francisco on June 30?

Platform comparison

Market context

On 30 June 2026, the San Francisco International Airport will record its highest daily temperature, a real-world event that determines the settlement of a prediction market currently implying zero probability for any outcome above 65°F. This 0% implied probability reflects a market consensus that extreme heat is virtually impossible, yet historical data suggests a more nuanced picture. Average June highs at KSFO typically climb from 68°F to 71°F, rarely dropping below 61°F or exceeding 80°F[3]. However, the first half of summer 2026 has been unusually cool, with the airport recording its coldest start since 1965 and an average maximum of just 67.6°F through mid-July[6]. This recent anomaly may be driving the current 0% pricing, but climate normals still show a 73°F maximum as the standard for this date, with a record of 92°F set in 1996[8][9].

Traders should monitor the National Weather Service’s daily climatological reports and Wunderground’s live hourly data, as these are the definitive resolution sources for the market[2]. The immediate catalyst is the diurnal temperature cycle, with current readings showing a high of 20°C (67°F) and a fresh westerly breeze of 18 mph, which typically suppresses extreme heat spikes[2]. While Polymarket often displays decimal odds and lower fees with minimal KYC, platforms like Kalshi and Betfair emphasise implied probabilities and stricter regulatory compliance, creating divergent liquidity dynamics for this specific weather event. The fee structures and KYC reach on these competing books mean that a sudden shift in the 7 PM temperature reading could trigger rapid arbitrage, particularly if the market fails to adjust to the 73°F climate normal[8].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We read Highest temperature in San Francisco on June 30? from four platform perspectives: Polymarket (on-chain CLOB), Kalshi (CFTC-regulated exchange), Betfair Exchange (sports book exchange), Smarkets (peer-to-peer betting exchange). Polymarket's live mid is the canonical probability; the side-by-side columns benchmark fees, KYC, settlement currency and deposit rails so you can choose the venue that fits your jurisdiction and trade size.

Resolution & payout

Settlement is the biggest difference between the four platforms: Polymarket on-chain in USDC (instant), Kalshi USD via CFTC (T+1), Betfair and Smarkets in local currency via bank withdrawal (T+1 to T+3). On-chain settlement clears in minutes — the fastest payout path of the four.

FAQ

Which platform has the deepest liquidity?

Polymarket — by a wide margin. Top markets reach $50-500M volume, Kalshi ~$200M cumulative, Betfair similar. Deeper liquidity means your trade moves the quote less.

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.

What about Smarkets as an alternative?

Smarkets is a UK betting exchange with a lower default commission (2%) than Betfair. Liquidity on political markets is below Polymarket, comparable to Kalshi. Geo-blocked in many jurisdictions.

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.

Which platform supports Klarna/SOFORT?

Directly: none. Polymarket accepts only USDC on Polygon. Polymarket Alternative offers a fiat on-ramp via Klarna or SOFORT (DE/AT/CH) and converts internally to USDC for the Polymarket order book. T+1 processing.