Highest temperature in London on August 11?

Platform comparison

Market context

On 11 August 2026, London City Airport's weather station will record the day's maximum temperature in Celsius, with traders currently pricing zero probability that it will fall into whichever range this market specifies. The settlement hinges on Weather Underground's Daily Observations table rather than the summary high-low figures, a distinction that matters when automated feeds occasionally diverge from granular station data. USDC holders on Polygon can currently acquire YES tokens at negligible cost, reflecting the crowd's conviction that August's London heat will stay below whatever threshold defines this contract's upper bound.

Historical August temperatures at London City Airport cluster between 18–26°C for daily highs, with readings above 28°C occurring roughly once per decade during the month. The 2022 heatwave pushed London to 40.3°C, though that was system-wide; City Airport's microclimate—influenced by the Thames and urban infrastructure—typically runs cooler than central London. The zero probability assigned here suggests traders expect a fairly typical summer day rather than an outlier event.

The UK Met Office publishes extended forecasts from mid-July onwards, and any significant weather pattern shift in early August could alter conditional token valuations. Tropical air masses occasionally push northward from continental Europe in mid-summer, though August typically sees more settled conditions than June or July. Traders monitoring Atlantic pressure systems and jet stream positioning in the weeks before settlement would capture early signals; current pricing reflects baseline expectations rather than any anticipated anomaly.

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

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

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 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.

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%.