Highest temperature in London on June 26?

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Market context

The underlying event is the peak temperature recorded at London City Airport on 26 June 2026, a date that has just passed with the settlement window closing at noon. Current prediction-market data shows a 0% implied probability for the "YES" outcome, suggesting the crowd believes the temperature will fall outside the specific range being traded, despite the day being observed as sunny with a high of 35°C at the station[2]. This stark divergence between the live weather observation and the zero probability line is unusual, as it implies a potential mispricing or a specific range definition that excludes the observed 35°C figure.

Historically, late June in London frequently sees temperatures exceeding 30°C, with the warm season running from mid-June to early September and average highs above 67°F[4]. Recent records support this trend, as the UK just broke its hottest June day record on 24 June, reaching 34.8°C, and the same day saw a maximum of 35.7°C at London City Airport[5][8]. These comparable cases indicate that a 0% probability for a range likely containing 35°C is statistically inconsistent with the established climate pattern and the immediate weather history of the past two days.

Traders should monitor the official Wunderground settlement data, which will confirm the exact maximum temperature for the day, as the current Met Office forecast for the following day also predicts a high of 33°C with thundery showers possible[1]. The key dependency is the precise definition of the temperature range in the market contract, as the observed 35°C high on 26 June sits near the upper threshold of typical June variability[2]. Any announcement regarding data corrections or station-specific anomalies from the National Weather Service could further explain the zero probability line, given the robustness of the 35.7°C reading from the NW3 Weather report[8].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). The odds column is filled only where we have clean data — that avoids the made-up numbers that get a network demoted when search engines cross-check against the source venue.

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

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.

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.