Highest temperature in London on August 19?

Platform comparison

Market context

On 19 August 2026, the highest temperature recorded at London City Airport will determine which range this contract settles into. The market currently prices all temperature bands at 0% YES, reflecting the standard state of unresolved future weather contracts on Polymarket before meaningful price discovery occurs. Settlement hinges on the Daily Observations table from Weather Underground rather than the Day High & Low summary—a distinction that matters when automated station readings occasionally diverge from rounded public-facing figures. USDC collateral on Polygon will be distributed across conditional tokens once the settlement window closes at midday UTC on the resolution date.

August temperatures at London City Airport typically cluster between 20–24°C, with historical highs rarely exceeding 28°C. The Met Office's 30-year average for mid-August peaks sits around 23°C, though the station has recorded 29.1°C in August 2022 during an exceptional heatwave. Current market pricing at 0% across all ranges suggests traders are awaiting atmospheric pattern clarity; early summer 2026 forecasts and any issued heatwave warnings from the Met Office will serve as primary catalysts for range selection. Traders should monitor the UK Health Security Agency's heat-health alert system in July and early August, as these trigger when models indicate sustained high temperatures, and track Atlantic weather systems that either deliver cooler maritime air or trap continental heat over the British Isles.

Methodology

We track Highest temperature in London on August 19? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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 Polymarket Scam?. 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%.