Highest temperature in London on June 25?

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Market context

The underlying real-world event is the highest temperature recorded at London City Airport on 25 June 2026, measured in degrees Celsius and resolved via Wunderground data. This single meteorological reading will determine the market outcome, with the settlement window closing at 12:00 UTC on the specified date.

Historical June temperatures in London typically peak around 21.3°C on 29 June, though recent anomalies have pushed records higher; Kew Gardens recorded 26.6°C in early 2026, marking the hottest day so far this year[3]. Just two days prior, NW3 Weather logged a maximum of 33.9°C on 23 June 2026, indicating that extreme heat events are already occurring in the region[7]. These comparable cases suggest that a 0% YES probability for any temperature range may be premature, as June 2026 has already demonstrated significant thermal volatility.

Traders should monitor upcoming Met Office forecasts for the bank holiday period, which previously predicted temperatures reaching 30°C[8], and watch for any official announcements regarding heatwave classifications or air quality alerts. The German GlüStV regulatory framework and US CFTC reach both impose compliance layers on prediction markets, yet the “no-KYC up to $1,500” threshold allows broader accessibility for retail participants without identity verification, making this market particularly open to non-professional traders. Recent news from Sky News confirms that London is already experiencing record-breaking warmth, reinforcing the need to reassess current crowd-implied probabilities[3].

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.

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 PolyGram?

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

Do I need to KYC for this market?

Not under $1,500 of lifetime trading volume. Above that threshold, PolyGram triggers a quick verification flow that finishes in minutes.