Highest temperature in London on August 8?

Platform comparison

Market context

The result depends on the highest **actual temperature** logged at London City Airport on 8 August, not the headline “day high” shown elsewhere on Weather Underground. In prediction-market terms, a **YES** share pays out if the temperature lands in the specified outcome range; a **NO** share wins if it does not, so the key question is which range contains the day’s top recorded Celsius value in the Daily Observations table.

The current **0% YES** price suggests traders think that outcome is effectively impossible, but that can simply reflect an outcome already seen in the data flow rather than a firm forecast. For context, London’s August averages are usually in the low 20s Celsius, with many historical days much cooler than heatwave extremes, yet the city can still produce high-20s or low-30s readings during warm spells.[5][10][12] August weather markets often hinge on brief afternoon peaks rather than the all-day impression shown in forecasts, so the exact station reading matters more than broad citywide averages.[7][12]

For traders watching the setup, the main catalyst is the station’s observation sequence through the settlement window, especially any late-morning to early-afternoon warm-up before the 12:00 UTC cutoff. A yellow heat-health alert was in force for London from 8 August, which points to elevated heat risk on the day, and third-party forecasts were already flagging a warm, sunny spell with highs around 29°C.[6][11] That said, only the Weather Underground Daily Observations table for London City Airport should decide the market, so the important dependency is the station’s recorded maximum, not the forecast headline.[6][11]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to Prediction Market UK, which mirrors the Polymarket order book directly.

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 Market UK. 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%.