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 of this market. The resolution hinges on Weather Underground's Daily Observations table rather than its Day High & Low summary—a methodological distinction that occasionally produces different readings depending on measurement timing and station calibration. This specificity matters: traders must verify which data source each platform uses for settlement, as Polymarket, Kalshi, Betfair, and Smarkets may reference different weather databases or interpretation protocols.

London's August temperatures typically range between 20–26°C, with extremes rare but documented. The 0% crowd probability suggests either extreme confidence in a narrow temperature band or sparse liquidity on this particular market. Historical August highs at London City Airport have occasionally exceeded 30°C during heat waves (notably August 2022 reached 40.3°C across the UK, though London City Airport recorded lower peaks). Comparable weather markets on major platforms show that temperature-range contracts often cluster probability mass around the most likely 2–3 degree bands, leaving tail outcomes underpriced relative to meteorological risk.

Traders should monitor the UK Met Office's long-range forecasts from late July onwards, particularly any heat-wave warnings issued in early August. The Atlantic Oscillation and jet-stream positioning in summer 2026 will influence whether continental high pressure systems dominate. Platform differences matter operationally: Kalshi's decimal odds format and KYC requirements differ from Betfair's fractional odds and lighter verification, whilst Smarkets' fee structure and Polymarket's settlement speed vary considerably. Each platform's historical accuracy on weather resolution—particularly disputes over measurement station data—should inform venue selection for this contract.

Methodology

This page compares Highest temperature in London on August 11? specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. The live probability is the Polymarket mid; the comparison columns summarise each venue's fee structure, KYC, settlement currency and payment rails. Every CTA routes to Robinhood Prediction Markets, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Polymarket settles via UMA Optimistic Oracle on Polygon. A proposer posts the outcome with a bond, the two-hour window runs, then the smart contract pays USDC.

Kalshi settles USD through the CFTC-regulated clearinghouse — the cleanest variant, with heavier KYC. Betfair Exchange settles in account currency (GBP/EUR), net of 2-5% commission. Smarkets follows the same model as Betfair with a lower default 2% commission.

FAQ

Polymarket vs Kalshi — which is better?

Depends on your location. Kalshi is CFTC-regulated, US-only with full KYC. Polymarket is global, on-chain, no KYC up to $1,500. Polymarket has ~10x higher liquidity but higher regulatory risk.

Which platform has the deepest liquidity?

Polymarket — by a wide margin. Top markets reach $50-500M volume, Kalshi ~$200M cumulative, Betfair similar. Deeper liquidity means your trade moves the quote less.

Is Betfair a Polymarket alternative?

Only partially. Betfair Exchange is UK-focused with a sports-betting emphasis; they have politics markets but with thinner liquidity than Polymarket. Settlement in GBP/EUR, 2-5% commission on winnings.

Are all these platforms regulated?

No. Kalshi is CFTC-regulated (US). Betfair and Smarkets are UK Gambling Commission licensed. Polymarket operates without explicit regulation — a different risk profile than a regulated sportsbook.

Which platform supports Klarna/SOFORT?

Directly: none. Polymarket accepts only USDC on Polygon. Robinhood Prediction Markets offers a fiat on-ramp via Klarna or SOFORT (DE/AT/CH) and converts internally to USDC for the Polymarket order book. T+1 processing.