Highest temperature in London on August 17?

Platform comparison

Market context

On 17 August 2026, London City Airport's weather station will record a daily maximum temperature. This market asks traders to predict which temperature range that reading will fall into. In prediction markets, a YES share pays out if the event occurs; a NO share pays out if it doesn't. Here, you're betting on whether the highest temperature will land in a specific band—say, 28–30°C—rather than a broader outcome. The crowd currently assigns zero probability to the YES position, suggesting either extreme confidence in an alternative range or insufficient liquidity to establish a baseline.

August temperatures at London City Airport typically cluster between 20 and 25°C, with occasional peaks above 27°C during heat waves. Historical data from the Met Office shows that readings exceeding 30°C in mid-August remain uncommon but not unprecedented; the 2022 heatwave saw temperatures breach 40°C across southern England, though London City Airport's readings tend to run slightly cooler than central London due to proximity to the Thames. The current zero probability likely reflects the market's assessment that extreme heat is unlikely in that particular week, anchored to long-term August averages rather than recent volatility.

Traders should monitor the European summer weather pattern forecast from mid-July onwards, particularly jet-stream positioning and any developing Atlantic ridge systems. The UK Met Office typically issues extended outlooks by early August that can shift market expectations sharply. Additionally, any unusual solar activity or volcanic aerosol effects reported by atmospheric monitoring agencies could influence seasonal temperature trajectories, though such factors rarely move individual-day forecasts more than a few days out.

Methodology

We track Highest temperature in London on August 17? 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 Prediction Market UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

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%.