Highest temperature in London on August 18?

Platform comparison

Market context

The market is pricing the highest temperature at London City Airport on 18 August 2026 at 0% probability across all temperature ranges, suggesting the crowd expects either missing data or a technical resolution issue rather than genuine uncertainty about the weather outcome. This extreme positioning reflects either a data-sourcing concern or a misunderstanding of the settlement mechanics rather than meteorological confidence.

August temperatures at London City Airport typically range between 18–24°C, with highs occasionally reaching 26–28°C during warm spells. Historical August records show the airport has recorded temperatures above 30°C only twice in the past two decades, making extreme heat scenarios genuinely rare but not impossible. The 0% crowd probability appears disconnected from actual climatological precedent; even conservative forecasting would assign non-trivial probability to moderate-to-warm outcomes (22–26°C range) that occur in roughly 60–70% of August days at the location.

The settlement hinges on Weather Underground's Daily Observations table for London City Airport specifically, not summary figures or other stations. Traders should verify that Wunderground maintains consistent historical data capture for this station through August 2026, as gaps or station maintenance could affect resolution. The two-year lead time means weather forecasting has minimal predictive value; the real driver is data availability and whether the crowd's 0% reflects genuine scepticism about data provision or a systematic mispricing of ordinary summer temperatures.

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 Who Will Win, which mirrors the Polymarket order book directly.

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.

UK Frequently Asked Questions

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 Who Will Win. 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.

Is Polymarket legal in the UK?

Polymarket is accessible to UK traders but is not UKGC-licensed. It operates under US CFTC jurisdiction. UK residents face no domestic legal prohibition on using it, but UKGC consumer protections do not apply. For UKGC-regulated alternatives, Betfair Exchange and Smarkets offer similar prediction-style markets.

Do I pay tax on prediction market profits in the UK?

UKGC-licensed platform profits (Betfair, Smarkets) are typically tax-free gambling winnings for UK individuals. Polymarket profits involve USDC crypto transactions, which HMRC treats as Capital Gains Tax events. Keep full transaction records and report via Self Assessment if gains exceed £3,000 per tax year.

How do I deposit on Polymarket from the UK?

UK traders typically fund Polymarket via Coinbase UK, Kraken or Revolut — buying USDC with GBP and transferring to a Polygon-compatible wallet (MetaMask, Coinbase Wallet). Polymarket's onboarding walks you through the bridging process. Typical GBP-to-USDC conversion costs 0.5–1%.