Highest temperature in London on August 7?

Platform comparison

Market context

Polymarket prices this contract at 0% for **22°C or below**, with the rest of the ladder centred on the mid-20s, so the on-chain market on Polygon is currently treating a very warm London reading as the base case rather than an outlier.[3] Because settlement uses the Weather Underground Daily Observations table for London City Airport, the relevant number is the highest observed Celsius reading recorded there by the noon UTC cutoff, not the broader forecast high shown elsewhere.[3]

That pricing sits against a summer that has already produced notable UK heat, including 26.6°C at Kew Gardens earlier in 2026, and official Met Office commentary that daily maximums have been running above seasonal averages.[7][15] For a London August reading, the main comparison is with ordinary seasonal warmth rather than extremes: long-run August norms for London are usually around the low 20s, while hotter spells can push the city into the high 20s or low 30s when continental air dominates.[11][12]

The main catalysts are short-range forecast updates and any late-morning temperature evolution at London City Airport, because the market resolves on a specific station and a specific observations table rather than a generic city forecast.[3] Traders on the conditional-token market should watch for revisions from the Met Office and commercial forecasters, plus live station data through the morning, since a 1°C move can shift the winning band quickly in a finely binned market settled in USDC.[4][12]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

Resolution & payout

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

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 Alternative UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

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%.