Highest temperature in London on June 26?

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Market context

The underlying event is the highest temperature recorded at London City Airport on 26 June 2026, with the market currently assigning a 60% probability to a 36°C outcome and 33% to 35°C, despite a separate crowd-implied 0% for a specific "YES" condition that likely refers to a narrower threshold not met by these leading ranges[1]. Historical precedents frame this probability: the June 2026 market for 6 June settled at 17°C under unsettled post-May conditions, whereas current forecasts suggest this week could break the 1976 record of 35.6°C, with temperatures projected to reach 37°C to 40°C under rare red alerts for extreme heat[2][3].

Traders should monitor the Met Office’s red alert schedule, which runs from 9 AM Wednesday to 9 PM Thursday, indicating a significant risk to life and severe pressure on public services as the heatwave peaks[3]. The resolution source is Wunderground’s daily history for London City Airport, and the market’s accessibility hinges on regulatory frameworks: German GlüStV implications and US CFTC reach define the legal boundaries, while the "no-KYC up to $1,500" provision allows retail participants to access this specific temperature market without identity verification, provided they stay within that threshold. Recent forecasts note "growing confidence" that this week will surpass the 1976 record, with southern regions expected to hit 37°C[3].

The market’s 60% frontrunner for 36°C reflects the intensity of the current heatwave, which may approach the all-time UK record of 40.3°C set in Lincolnshire in July 2022[3]. Dependencies include the stability of the Wunderground data feed and the Met Office’s warning validity, as the resolution window ends at 12:00 UTC on 26 June. The 0% crowd-implied probability for the "YES" condition likely stems from a mismatch between the condition’s definition and the leading 35–36°C ranges, not a lack of heat.

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

Where can I trade this market with the lowest fees?

On Polymarket Legal 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 Polymarket Legal UK?

Zero. Polymarket Legal 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.