Highest temperature in London on August 19?

Platform comparison

Market context

On 19 August 2026, the highest temperature recorded at London City Airport will determine which range this market resolves to, with settlement based on the Daily Observations table from Weather Underground rather than summary figures. The crowd currently assigns zero probability to any outcome, suggesting either insufficient liquidity or genuine uncertainty about temperature bands not yet priced in across competing platforms.

London's August temperatures have historically clustered between 20–27°C, with extremes rare but documented. The Met Office records show that temperatures exceeding 30°C occur roughly once per decade in August, whilst readings below 15°C are uncommon. The 2022 heatwave pushed London to 40.3°C in July, though August typically runs cooler. Cross-platform comparison reveals sportsbooks do not typically price weather outcomes, leaving prediction markets as the primary venue; however, the 0% crowd probability suggests either range definitions that traders find implausible or a market awaiting initial price discovery. Analyst consensus from the Met Office's seasonal outlooks will become relevant as summer 2026 approaches, though such forecasts carry substantial uncertainty beyond six months.

Traders should monitor the Atlantic Oscillation index and sea-surface temperatures in the North Atlantic through spring and early summer 2026, as these influence August weather patterns over the UK. The UK Health Security Agency's heat-health alert system, typically activated in July, may signal whether conditions favour above-average temperatures. Any significant divergence between early-summer forecasts and historical August norms could trigger repricing across prediction markets once liquidity materialises.

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 Kalshi vs Polymarket, 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.

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 Kalshi vs Polymarket. 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.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

Do I need to KYC for this market?

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