Highest temperature in London on August 11?

Platform comparison

Market context

On 11 August 2026, the highest temperature recorded at London City Airport will fall within one of several defined ranges. The market resolves using the Daily Observations table from Weather Underground rather than summary figures, a distinction that matters when intraday peaks diverge from reported highs. For programmatic traders, this means building a data pipeline that polls the specific table endpoint rather than relying on API summary fields, which often lag or smooth readings. The settlement window closes at midday UTC, creating a hard cutoff that requires monitoring through the morning hours.

London's August temperatures have historically clustered between 20–25°C, with excursions above 28°C occurring roughly once per decade. The 2022 heatwave pushed readings to 40.3°C at nearby stations, but such extremes remain statistical outliers. Current crowd probability sitting at 0% suggests either a specific temperature threshold has been set high enough to be climatologically unlikely for that date, or the market structure itself has created a resolution ambiguity that participants are pricing defensively. Comparable August markets from prior years show that when thresholds exceed the 90th percentile, crowd confidence collapses even when meteorological conditions remain plausible.

Traders should monitor the Met Office's extended forecast from late July onwards, particularly any heat dome positioning over the British Isles. The UK Health Security Agency typically issues heat-health alerts 2–3 days ahead of sustained warmth, providing a leading indicator. Conditional orders tied to specific forecast updates—such as triggering buys if the 10-day outlook shifts above 26°C—would allow hands-off position management through the settlement window.

Methodology

This page reviews Highest temperature in London on August 11? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Polymarket Bot UK, which mirrors the Polymarket order book at 0% fees.

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 Polymarket Bot 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.

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%.