Highest temperature in London on August 16?

Platform comparison

Market context

On 16 August 2026, London City Airport's weather station will record a daily maximum temperature. The market settles on whichever temperature band captures that peak reading, drawn from Weather Underground's Daily Observations table rather than summary figures—a distinction that matters when automated stations report granular data differing from rounded day-high summaries. Currently priced at 0% YES across all ranges on Polygon, the contract reflects genuine uncertainty about which bracket will contain the actual high, though the 0% reading suggests traders are either awaiting historical baseline data or treating this as a placeholder until closer to settlement.

August temperatures at London City Airport typically peak between 20–24°C, with extremes occasionally reaching 26–28°C during heat waves. The 2022 summer heatwave saw London record 40.3°C, though City Airport—situated on the Thames estuary with moderating maritime influence—rarely matches inland peaks. Historical August averages cluster around 22°C, providing a reference point for assessing which ranges carry genuine probability mass versus tail-risk pricing.

Traders should monitor the Met Office's medium-range forecasts from early August 2026 onwards, particularly any alerts for high-pressure systems or Atlantic blocking patterns that could drive anomalous heat. The UK Health Security Agency's heat-health alerts, typically issued 2–3 days ahead of significant warming, often correlate with temperature spikes at major monitoring stations. Seasonal atmospheric patterns—including the North Atlantic Oscillation phase and jet-stream positioning—will determine whether August 2026 runs warm or cool relative to the 30-year baseline.

Methodology

We track Highest temperature in London on August 16? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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.

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 Scam?. 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.

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%.