Highest temperature in London on June 25?

Platform comparison

Active sub-markets

Market context

London is currently experiencing a significant heatwave, with temperatures soaring well above seasonal norms and breaking multiple records just days before the market’s settlement date. On 23 June, Hampstead recorded a maximum of 33.9°C, while Gatwick saw a provisional June record of 37.5°C, and Heathrow hit 37.8°C [8][9]. This intense warmth has already pushed June temperatures into territory that historically rivals or exceeds the warmest days of the year at London City Airport, where the average daily high during the warm season (16 June to 8 September) is just 67°F (19.4°C) [1].

Historically, London City Airport rarely exceeds 30°C in June, with the warmest month typically being August. However, the current spell of extreme heat—marked by southerly winds, low humidity, and clear skies—suggests a high likelihood of temperatures entering the 30–35°C range on 25 June, directly contradicting the crowd-implied 0% probability for any outcome above the lowest range [2][5]. Traders should monitor official Met Office updates and Wunderground’s hourly data for London City Airport (EGLC) as the day progresses, particularly the 17:00 BST reading, which often captures the daily peak [6][7]. Any further escalation in heat, especially with sustained southerly flow, could push temperatures toward 35°C or higher, making the current market pricing appear severely misaligned with real-world conditions.

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 PolyGram — the application we operate, where you trade directly against the Polymarket order book at 0% fees.

Resolution & payout

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

FAQ

Where can I trade this market with the lowest fees?

On PolyGram, 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.

Is this market available outside the US?

PolyGram is available in most jurisdictions where Polymarket isn't directly accessible. Polymarket itself is geo-blocked in the US/UK/EU. Always check local regulations.

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.