Highest temperature in London on August 13?

Platform comparison

Market context

The market concerns the highest temperature recorded at London City Airport on 13 August 2026, with settlement based on Weather Underground's Daily Observations table rather than summary figures. The 0% implied probability reflects the market's current assessment that no specific temperature threshold has been set as the resolution target, leaving traders without a defined upper bound to price against. This structural ambiguity distinguishes the contract from typical weather markets, where ranges are pre-specified.

August temperatures at London City Airport historically peak between 20–24°C, with extremes rarely exceeding 28°C. The station's location near the Thames and exposure to maritime air masses moderates heat compared to inland London sites. The hottest August day on record for the broader London area occurred in 2022, when temperatures reached 40.3°C, though City Airport's readings typically run 3–5°C cooler due to its riverside position. Traders should reference the Met Office's historical station data for London City Airport to establish realistic bounds for the settlement window.

The UK's summer weather patterns depend on Atlantic pressure systems and potential heat domes from continental Europe. The Met Office's seasonal outlook, typically issued in June 2026, will provide the first formal guidance on August conditions. Any significant warming pattern emerging in late July could shift expectations materially. Traders should monitor the European Centre for Medium-Range Weather Forecasts (ECMWF) extended forecasts from early August onwards, as these offer the most reliable 10–14 day guidance for London's specific microclimate.

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

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.

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.

Do I need to KYC for this market?

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