Highest temperature in London on August 14?

Platform comparison

Market context

On 14 August 2026, the highest temperature recorded at London City Airport will determine the settlement range for this market. The crowd currently assigns zero probability to any outcome, suggesting either incomplete market formation or an expectation that the event will fall outside all offered ranges. Resolution hinges on the Daily Observations table from Weather Underground rather than headline figures, a distinction that matters when intraday peaks differ from official daily summaries.

August temperatures at London City Airport typically peak between 20–24°C, though the station's riverside location and urban heat island effects create variability. Historical August records for the site show occasional excursions toward 26–28°C during heatwaves, but such extremes occur roughly once per decade. The zero probability reading suggests the market may be pricing in either a narrow range of offered brackets or genuine uncertainty about whether the settlement mechanism will function as specified. Comparable August dates in recent years have seen highs in the 21–23°C band, making mid-range outcomes statistically more frequent than either cold snaps or exceptional heat.

Traders should monitor the Met Office's medium-range forecasts from late July onwards, particularly any signals of continental high pressure systems or Atlantic low-pressure troughs that could drive August conditions significantly above or below seasonal norms. The UK's summer weather patterns remain sensitive to North Atlantic Oscillation phases and jet stream positioning, both of which can shift materially in the fortnight before settlement. Any early August heatwave warnings or unseasonal cold spells would sharpen the probability distribution considerably.

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

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

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%.