Highest temperature in London on August 15?

Platform comparison

Market context

On 15 August 2026, the highest temperature recorded at London City Airport will fall into one of several defined ranges, measured in degrees Celsius via Weather Underground's Daily Observations table. The market currently prices all YES outcomes at 0%, suggesting traders view the contract specifications or settlement mechanics as presenting material friction. This disconnect between theoretical event probability and market pricing warrants scrutiny before deploying USDC on Polygon's conditional token structure.

London's August temperatures historically cluster between 20–24°C for daily highs, with extremes rare but documented. The Met Office records show August 2022 peaked at 40.3°C during an exceptional heatwave, whilst typical August days see highs around 21–23°C. The 0% pricing likely reflects either low conviction in extreme outcomes or uncertainty around the Weather Underground Daily Observations data source—which differs from standard Met Office reporting and introduces basis risk for traders unfamiliar with that platform's measurement protocols.

Traders should monitor the UK's summer weather patterns from June onwards, particularly Atlantic ridge positioning and any European heat systems tracking northwestward. The Met Office's seasonal outlooks, published quarterly, will provide early signals about August 2026 temperature likelihood. Additionally, the precise settlement window closing at 12:00 UTC on 15 August matters operationally; any temperature spike occurring after noon would not be captured, creating a timing dependency that distinguishes this contract from broader climate forecasts. Conditional token mechanics on Polygon mean positions cannot be unwound post-settlement, so clarity on the exact measurement window is essential before entry.

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 Kalshi 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

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

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%.