Highest temperature in London on July 3?

Platform comparison

Market context

The real-world event is the highest temperature recorded at London City Airport on 3 July 2026, a date that historically sits within London’s warmest month. While average July highs hover around 23°C, Met Office data confirms that heatwaves frequently push temperatures above 30°C, with a record 40.2°C reached at nearby Heathrow in July 2022[1]. Current crowd-implied probability for a specific high-temperature range sits at 0% YES, a stark divergence from the 45.5% implied probability for a low-temperature threshold of 15°C on the same date in a parallel market[3]. This suggests the crowd is either mispricing the volatility of summer extremes or betting on a specific cool anomaly despite historical trends favouring sustained scorchers in 2026[1].

Traders must monitor the Met Office’s daily forecast updates and the southerly wind flow currently driving humidity to 88% at the airport, which can amplify perceived heat even if thermometers lag[2]. The immediate catalyst is the 26°C high forecast for Friday 3rd July, which aligns with recent daily peaks of 26.4°C recorded on 2 July[2][9]. Analysts should watch for any sudden shifts in the falling pressure trend (1012mb) that could disrupt the current warm spell, as well as the 16-hour daylight window that maximises solar heating potential[1]. The resolution source, Wunderground, will capture the precise peak, making the 26°C forecast a critical benchmark against which the 0% market probability will be tested[1].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to Best Prediction Markets, which mirrors the Polymarket order book directly.

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 Best Prediction Markets. 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.

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'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.