Highest temperature in London on July 7?

Platform comparison

Market context

The underlying event is the highest temperature recorded at London City Airport on 7 July 2026, measured in degrees Celsius and sourced from Wunderground. Current crowd-implied probability sits at 0% for a specific range, suggesting the market expects no extreme heat spike for that date, though today’s actual high of 31°C [2] shows summer warmth is already present.

Historically, July is London’s hottest month, with an average high of 22°C (72°F) at this station [6], and 2022 marked the first time London exceeded 40°C on 19 July [8]. However, that record was an outlier driven by a rare continental heat dome; typical July highs at London City Airport rarely breach 30°C, making the 0% probability for extreme ranges plausible unless a new atmospheric anomaly develops.

Traders should monitor Met Office forecasts for developing heat domes or southerly wind shifts, which can rapidly elevate temperatures [4]. The key catalyst is the arrival of a high-pressure system from the south, a pattern seen in recent years that pushed highs to 31°C [2]. While no official announcement has been made for 7 July, the Met Office’s 14-day forecast [1] and AccuWeather’s July 2026 projection [5] indicate daily highs between 21°C and 36°C, meaning the market’s 0% stance hinges on the absence of a sudden, unprecedented heatwave. Programmatic approaches would feed Wunderground’s real-time API into conditional orders, triggering trades only if temperatures breach 32°C before settlement.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on July 7? 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

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.

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.

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.