Highest temperature in London on July 7?

Platform comparison

Market context

The underlying real-world event is the daily maximum temperature recorded at London City Airport on 7 July 2026, with the Met Office forecasting a heatwave peaking at 34°C earlier in the week and sustaining highs no lower than 32°C through mid-July. On Polymarket, this contract currently prices the 31°C outcome at 68% probability, having generated $106.8K in volume since launch, while the 30°C outcome sits at 19%[1]. The crowd-implied 0% probability for a "YES" resolution appears to stem from a misunderstanding of the market’s binary structure, as the actual trading focus is on the specific temperature range rather than a simple yes/no condition.

Historical July heatwaves in London, including the 2022 event that reached 40°C, show that sustained high temperatures above 30°C are common when yellow heat alerts are issued, as the UKHSA has done for London from 4 July to 11 July 2026[2]. The current forecast suggests the heatwave will last until at least Sunday, with daytime highs consistently exceeding 30°C for up to 10 consecutive days, making a 31°C peak on 7 July highly plausible given the trend[2].

Traders should monitor the Met Office’s daily updates for any sudden shifts in temperature or the arrival of isolated thunderstorms, which the forecast notes could develop as heat intensifies between 5–7 July[4]. The resolution source is Wunderground’s recorded daily maximum for London City Airport, and any discrepancy between forecasted and actual readings could alter the outcome, so real-time data from the Met Office and BBC Weather at EGLC is critical[5][8]. The settlement window ends 12:00 UTC on 7 July 2026, and all trades are settled in USDC on the Polygon network using conditional tokens.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in London on July 7? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Kalshi UK, which mirrors the Polymarket order book at 0% fees.

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 UK. 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.