Highest temperature in London on July 21?

Platform comparison

Market context

On 21 July 2026, the highest temperature recorded at London City Airport will fall into one of several defined ranges. A YES share in this market pays out if the actual temperature lands within your chosen bracket; a NO share pays if it lands elsewhere. The settlement hinges on historical weather data from Wunderground, which logs hourly readings throughout the day. Traders are essentially wagering on whether London will experience a heatwave, mild summer conditions, or something cooler than average for late July.

London's July temperatures have historically clustered between 20°C and 25°C, with extremes rare but documented. The record high for July in London stands at 40.3°C, set in 2022 during an exceptional heatwave. More typical peak days in mid-to-late July see maxima around 23–24°C. The 0% crowd probability on all ranges suggests either a data-loading issue or genuine uncertainty about which bracket will resolve. Comparable markets on UK summer temperatures have shown traders gravitating toward mid-range outcomes (22–26°C bands) when historical volatility is factored in.

The UK Met Office publishes seasonal outlooks and extended forecasts that traders should monitor as July 2026 approaches. Any official warnings of unusual pressure systems or Atlantic weather patterns could shift expectations. Soil moisture conditions and spring rainfall in 2026 will influence summer heat retention. Traders should cross-reference Wunderground's historical data for London City Airport specifically, as microclimatic differences mean readings there can differ from central London or other stations by 1–2°C on any given day.

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to Prediction Market UK, which mirrors the Polymarket order book directly.

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 Prediction Market UK. 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.

Do I need to KYC for this market?

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

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.