Highest temperature in London on August 11?

Platform comparison

Market context

On 11 August 2026, the highest temperature recorded at London City Airport will determine the settlement range for this contract. The market currently shows zero implied probability across all ranges, suggesting either insufficient liquidity or consensus that no single temperature bracket warrants meaningful odds. This stands in sharp contrast to typical August weather markets, where sportsbooks and meteorological services routinely price temperature bands with measurable probability mass distributed across multiple outcomes.

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; the 2022 heatwave reached 40.3°C at nearby stations, though such events remain statistical outliers. Historical volatility in August settlement outcomes suggests that zero probability across all ranges reflects market dysfunction rather than genuine certainty about the day's conditions. Comparable weather markets on other platforms typically assign non-zero probabilities to the 20–25°C and 25–30°C bands as baseline positions.

Traders should monitor the Met Office's extended forecast as August approaches, particularly any signals of Atlantic blocking patterns or heat dome development. The UK's summer weather dependency on North Atlantic Oscillation indices and jet stream positioning means that forecasts issued in late July will carry substantially more predictive weight than current assessments. Recent seasonal outlooks from the European Centre for Medium-Range Weather Forecasts will inform whether 2026's August tracking follows cooler or warmer climatological tendencies, directly affecting which temperature ranges warrant non-zero pricing.

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.

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 Best Prediction Markets. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

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.