Highest temperature in London on August 21?

Platform comparison

Market context

The market seeks to establish the highest temperature recorded at London City Airport on 21 August 2026, measured in degrees Celsius and sourced from Weather Underground's Daily Observations table. The settlement window closes at midday on that date, meaning the resolution will capture the peak temperature achieved during the morning and early afternoon hours.

London's August temperatures have historically ranged between 20°C and 28°C, with extreme highs above 30°C occurring only in exceptional circumstances. The Met Office records show that temperatures exceeding 32°C in London during August are rare events, typically occurring once or twice per decade during heat waves driven by continental air masses. The current crowd probability of 0% suggests traders are pricing in a baseline expectation aligned with typical late-summer conditions rather than anomalous heat. August 2022 saw London reach 40.3°C during an exceptional heat event, but such extremes remain statistical outliers when assessing any single future date.

Traders monitoring this market should track seasonal forecasting models released in the weeks preceding late August 2026, particularly outputs from the UK Met Office and European weather centres regarding high-pressure systems and potential heat waves. The North Atlantic Oscillation index and sea-surface temperature anomalies in the Atlantic will influence whether continental warming patterns develop. Real-time weather forecasts become actionable only in the final fortnight before the settlement date, at which point meteorological confidence improves substantially. Any declaration of an amber or red heat-health alert by the UK Health Security Agency would signal elevated temperature probabilities warranting position reassessment.

Methodology

Political prediction markets differ structurally from sports betting: thinner liquidity, longer settlement windows, higher sensitivity to single news events. This page shows the live Polymarket quote for Highest temperature in London on August 21? plus platform attributes for the three reference venues, so you can see at a glance where the deepest market for this question sits.

Resolution & payout

Political markets typically settle on official candidate or agency confirmation. Polymarket uses UMA Optimistic Oracle: a proposer posts the outcome with a bond, the two-hour window opens, then the smart contract pays USDC.

Kalshi settles USD via CFTC clearinghouse, with clearly defined resolution sources (e.g. AP race calls for elections). Betfair settles after the official outcome is registered with the league or agency. Manifold is play-money.

UK Frequently Asked Questions

How accurate are political prediction markets?

Historically more accurate than polls. Polymarket's Brier score on US 2024 elections was ~0.11 — better than 538 (~0.14) and every mainstream poll. Markets aggregate information with real skin in the game.

Can prediction markets influence election outcomes?

Markets reflect expectations rather than create them. Studies show public-facing markets can anchor expectations, but don't influence the underlying outcome. Political markets are information, not advocacy.

Which platform has the deepest political liquidity?

Polymarket — by far. US 2024 presidential volume was ~$3.5B vs Kalshi (~$200M) and Betfair (~$120M). Where Polymarket is geo-blocked, brokers like Trump Prediction route into the same order book at 0% fees.

Why do Polymarket and Kalshi differ on elections?

Kalshi must follow CFTC compliance — strict definitions, clear resolution sources, US citizens only with KYC. Polymarket operates globally without CFTC oversight — deeper liquidity, but also higher regulatory risk.

Are UK election prediction markets available from the UK?

Yes. Betfair Exchange and Smarkets offer UKGC-regulated UK election markets (seat counts, party share, constituency results). Polymarket also lists UK election contracts with deeper global liquidity. Betfair winnings are typically tax-free for UK individuals; Polymarket profits are subject to HMRC CGT.