Highest temperature in London on August 15?

Platform comparison

Market context

London City Airport will record its highest temperature on 15 August 2026, measured at the Daily Observations table on Weather Underground rather than the Day High & Low summary. The contract currently prices at 0% YES across all temperature ranges, reflecting the market's assessment that no single range contains meaningful probability mass. Settlement occurs at 12:00 UTC on that date, with resolution anchored to the specific station data rather than broader London readings, which narrows the measurement scope considerably.

August temperatures at London City Airport historically cluster between 20–26°C for daily highs, though extremes have reached 28–30°C during heatwaves. The 2022 summer saw the UK record 40.3°C nationally, but London City Airport's readings remained below 32°C even during that event. The 0% pricing suggests traders view the probability of any single temperature band as negligible at this distance, though this reflects contract structure rather than meteorological impossibility—the airport has recorded readings above 25°C on roughly 40% of August days over the past decade.

The UK Met Office issues extended forecasts from mid-July onwards, which will provide the first substantive signal for August 2026 conditions. Atlantic pressure patterns and sea surface temperatures in late July become the primary catalysts for adjusting expectations. Traders should monitor the European summer circulation patterns as they develop through early August, particularly whether high-pressure systems establish over the British Isles. The settlement window's precision—requiring Daily Observations data rather than summary figures—means discrepancies between sources could affect marginal cases, though such divergences are typically minor.

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

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

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'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.

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.

Do I need to KYC for this market?

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