Highest temperature in London on August 11?

Platform comparison

Market context

The Met Office will record the peak temperature at London City Airport on 11 August 2026, with resolution determined by the Daily Observations table on Weather Underground rather than summary high-low figures. The 0% crowd probability suggests traders are pricing near-zero conviction that any specific temperature band will be the highest recorded that day, a reflection of the market's nascent state rather than meteorological certainty. August in London typically peaks between 20–24°C, though extremes have reached 28–30°C during heatwaves; the 2022 summer saw temperatures exceed 40°C across parts of southern England, establishing that outlier scenarios remain physically plausible.

Historical August temperature distributions at London City Airport show clustering around 21–23°C as modal outcomes, with roughly 15–20% of years recording highs above 25°C. The 2003 European heatwave and 2019 July peak of 38.7°C in Cambridge demonstrate that whilst rare, significant deviations from the 30-year mean occur within decadal timeframes. Current long-range forecasting models for summer 2026 remain unreliable; the UK Met Office typically issues seasonal outlooks only 3–4 months ahead, meaning actionable forecast data will not emerge until May 2026 at earliest.

Cross-platform comparison reveals minimal trading activity on competing venues, with Polymarket and Kalshi showing similarly sparse liquidity. No major weather-forecasting announcements or climate pattern shifts are scheduled to move odds materially before late spring 2026. Traders monitoring this contract should await the Met Office's May–July seasonal updates and any Atlantic circulation anomalies signalled by the North Atlantic Oscillation index.

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 Kalshi vs Polymarket. 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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Kalshi vs Polymarket trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.