Highest temperature in London on July 10?

Platform comparison

Market context

On 10 July 2026, London City Airport will record its peak temperature for the day, a single data point that determines the outcome of a prediction market where the crowd currently assigns zero probability to any temperature range above the lowest threshold. This event is not speculative; it is a physical measurement captured by meteorological sensors and published by Wunderground, the designated resolution source for the market.

Historically, July is London’s hottest month, with average highs at London City Airport reaching 22°C (72°F)[1], yet extreme heatwaves have pushed temperatures well beyond this baseline. In July 2022, several UK airports recorded 40°C for the first time in English history, a benchmark that redefined expectations for summer extremes[7]. More recently, a brief but intense heatwave in the third week of July 2025 saw temperatures surge across the British Isles, demonstrating that 0% crowd-implied probability may reflect a failure to account for such volatility rather than genuine climatic certainty[10].

Traders approaching this market programmatically should monitor real-time forecasts from the Met Office and AccuWeather, which currently predict 85°F (29.4°C) for 10 July with mostly sunny conditions and very warm temperatures[3][2]. Key catalysts include the timing of the south-easterly wind flow and the absence of cloud cover, both of which amplify surface heating. The National Weather Service confirms current conditions at London City Airport include 13°C with falling pressure and moderate visibility, suggesting dynamic atmospheric shifts that could alter the day’s peak[8]. Any sudden change in wind direction or the arrival of a high-pressure ridge could trigger a rapid temperature spike, making the 0% probability a potentially fragile position.

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.

FAQ

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 Fees. 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.

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.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.