Highest temperature in London on August 8?

Platform comparison

Market context

London’s settlement will be driven by the highest **daily observation** at London City Airport, not the headline Day High figure, so the practical task is to watch the station feed for the final published datapoint before the 12:00 UTC cut-off. In programme terms, this is a simple range-mapping problem: ingest the observed maximum, convert it into the market’s Celsius band, and only treat the result as final once Weather Underground stops revising that day’s table after the next-date datapoint appears. The crowd pricing at **0% YES** leaves the market effectively assigned to a non-target band, which is unusual when the underlying weather looks warm rather than exceptional.[1]

Recent comparable cases suggest these temperature markets are usually settled by a narrow band close to the forecast high, with the London 6 August market resolving cleanly to **23°C** after the station data confirmed the day’s maximum.[17] For 8 August, third-party forecasts pointed to a warm, sunny day around **28°C** in London, while general climate references for August still place the city near the low 20s on average, so the main question is whether the airport reading lands at the forecast peak or one band lower.[4][12][14]

The main catalysts are forecast updates, any change in the Met Office/airport observation pattern, and the timing of the final daily observation on Weather Underground. UKHSA had already put a **heat-health alert** in force for London from 8 August morning through 11 August evening, which underscores that the broader setup was hot enough to keep traders focused on whether the airport sensor would register an isolated spike or merely a high-20s plateau.[9]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on August 8? 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 Review UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

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%.