Highest temperature in London on July 20?

Platform comparison

Market context

London City Airport recorded its highest temperature on 20 July 2026, with the market now locked on the outcome. The crowd-implied probability for a YES result on any range above 25°C sits at 0%, while the 25°C bracket commands a 100% share, making it the undisputed favourite. This pricing reflects a consensus that the day will not breach the mid-20s, despite historical data showing London frequently experiences heatwaves pushing temperatures above 30°C, including the record 40.2°C at Heathrow in July 2022 [3]. Average July peaks hover around 23°C, yet the Met Office notes that sustained scorchers are common, suggesting the current 0% probability on higher ranges may be an underdog mispricing if a late heat spike occurs.

Traders should monitor the Met Office’s weekly heatwave forecasts and any sudden shifts in southerly wind patterns, which currently sit at 8 mph with 88% humidity at the airport [2]. A key catalyst is the upcoming release of the UK’s seasonal outlook, which could confirm whether 2026 will deliver the predicted sustained scorcher climbing well above 30°C [3]. Contrarian value likely sits in the 28–30°C or 30°C+ ranges, where the market’s 0% pricing ignores the frequency of recent heat events. With settlement ending 2026-07-20T12:00:00Z, the window for adjusting positions is narrow, and any announcement of a heat alert before noon UTC could trigger a sharp reprice away from the 25°C favourite.

Sources: 1 · 2 · 3

Methodology

This page reviews Highest temperature in London on July 20? 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 Who Will Win 2026, 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 Who Will Win 2026. 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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Who Will Win 2026 trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.

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.