Highest temperature in London on June 25?

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Market context

The highest temperature recorded at London City Airport on 25 June 2026 will determine the market outcome, with current on-chain pricing showing a 0% probability for the "YES" outcome on the 26°C or below range. Polymarket users trading USDC on the Polygon network see the frontrunner as 30°C at 27%, followed closely by 31°C at 25%, reflecting conditional token liquidity that prices in a significant heat event rather than cool conditions.

Historical June data frames this low probability for cool temperatures, as London City Airport typically experiences average daily highs above 67°F during the warm season from mid-June to early September, with recent records showing spikes to 40°C in extreme heatwaves. The 23 June 2026 daily report from NW3 Weather recorded a maximum of 33.9°C at Hampstead, just 12 miles from the airport, suggesting that temperatures well above 26°C are the norm rather than the exception for this period.

Traders should monitor the Met Office's amber alert for extreme heat, which has been extended through Thursday, and watch for scheduled updates on the Wunderground resolution source once the first data point for 25 June is published. The Standard reported on 24 June that temperatures could reach 40°C in the coming days, with an amber alert extended until at least the end of Thursday, indicating that the catalyst for a high-temperature outcome is already active in the forecast.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in London on June 25? across five venues. We show live odds for Polymarket-based markets (sourced from the Polygon order book); for other venues we list platform attributes, since the comparable contracts are not exposed via a public API on every venue. Every CTA points at Kalshi UK — the application we operate, where you trade directly against 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?

On Kalshi UK, which mirrors the Polymarket order book at 0% fees. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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 it cost to trade on Kalshi UK?

Zero. Kalshi UK routes every order to the live Polymarket order book; the only cost is the Polygon network fee, typically under $0.01 per transaction.

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.