Highest temperature in London on August 7?

Platform comparison

Market context

London’s temperature profile has shifted little in the last 24–48 hours: the latest forecasts still point to a dry, sunny afternoon with highs clustered in the mid-20s Celsius, rather than anything resembling a heat spike. AccuWeather’s August outlook for London shows daily highs mostly between 67°F and 78°F, while multiple day-specific forecasts for 7 August land around 22°C to 26°C, with little or no rain and light winds[1][3][4][6].

That leaves the market’s **0% YES** reading easy to understand in context. For London on 7 August, the comparable case is a normal summer day, not an extreme one: long-run August averages sit around the low 20s Celsius, and the day-specific guidance from several forecast providers is consistent with a top temperature in the low-to-mid 20s, well below any threshold that would require a notable heat event[11][15][3]. In other words, the current pricing reflects the absence of a catalyst for an exceptional reading at London City Airport rather than a judgement on small hourly fluctuations.

The main things traders can still watch are the afternoon evolution of cloud cover, the timing of any sea-breeze effect, and whether updated station observations at London City Airport run a degree or two warmer than model guidance. The Met Office’s afternoon briefing has also pointed to broadly dry conditions across southern England, with the warmest temperatures concentrated in the southeast, which supports the idea that the day’s peak should arrive in the early-to-mid afternoon rather than late evening[7][14]. Since settlement depends on the highest figure in Weather Underground’s Daily Observations table, the only meaningful move now would be an unexpectedly strong late-day spike in the station record[14].

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

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.

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%.