Highest temperature in London on August 12?

Platform comparison

Market context

On 12 August 2026, the highest temperature recorded at London City Airport will determine which temperature band this contract settles into. The market currently prices all outcomes at 0% YES, reflecting either a technical listing issue or extreme confidence that no single temperature range will occur—an unusual state for a weather contract with defined resolution bands. Polymarket's USDC settlement on Polygon means traders holding conditional tokens need clarity on which specific range brackets exist before committing capital, as the absence of visible YES probability suggests the market interface may not yet display the full range of outcomes available for trading.

Historical August temperatures at London City Airport show considerable variation. The station recorded 37.9°C on 19 July 2022 during the exceptional heatwave, whilst August highs typically range between 20–27°C. The Met Office's 30-year climate normals place the August mean maximum at approximately 23°C. This baseline matters because traders must distinguish between plausible but extreme scenarios (above 30°C) and more probable moderate outcomes (22–26°C), each carrying different risk profiles on-chain.

The UK Met Office publishes extended forecasts from mid-July onwards, with increasing confidence from early August. Traders should monitor the Atlantic pressure patterns in late July, as these determine whether warm continental air reaches south-east England or cooler maritime conditions prevail. The Environment Agency's drought status and any heat-health alerts issued in early August would signal elevated temperature risk. Weather Underground's Daily Observations table, specified as the resolution source, updates continuously and occasionally differs from summary highs—a technical detail that could affect settlement disputes if temperatures cluster near range boundaries.

Methodology

This page reviews Highest temperature in London on August 12? 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 Kalshi UK, which mirrors the Polymarket order book at 0% fees.

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

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

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%.