Highest temperature in London on August 9?

Platform comparison

Market context

London has just moved into a renewed hot spell after a cooler start to the day, with late updates on 9 August pointing to daytime peaks in the high-20s to low-30s across the capital. Recent reporting on the broader UK heat pattern says high pressure re-established over southern and central Britain over the weekend, with London and the South East reaching around 31–32°C on 9 August, while WeatherSpark’s latest Heathrow-area observation still showed 63°F at 01:20 UTC, underscoring how quickly the afternoon could climb from an unremarkable overnight baseline.[2][1]

That setup makes the current 0% implied probability on the exact range outcome easier to read as a reflection of how tightly traders are clustering around the forecast peak, rather than a signal that heat is absent. August in London can produce sharp intraday swings, and recent 2026 heatwave coverage already shows the city’s temperatures pushing well above normal, with Kew Gardens hitting 26.6°C earlier in the summer and southern England repeatedly printing 30°C-plus days this month.[10][2] For this market, the relevant question is not the displayed daily high in a summary box, but the highest value in Weather Underground’s daily observations for London City Airport, which can be nudged by a brief mid-afternoon spike even if surrounding readings stay lower.[3]

The main catalysts to watch are the same-day forecast evolution, any afternoon cloud or convection over Greater London, and the first hourly observations that can confirm whether London City Airport edges into the 31°C band or stalls below it. Forecast reporting today has centred on sunny skies, light winds, and negligible rain risk, which supports a warmer ceiling, but small changes in wind direction or sea-breeze penetration can trim the peak by a degree or more.[3][4] Traders also need to watch the station feed itself, because this market settles on the recorded observation sequence for the airport, and late revisions remain relevant until the next day’s first datapoint appears.[3]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in London on August 9? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Prediction Today, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

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 Prediction Today. 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%.