Highest temperature in London on June 27?

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Active sub-markets

Market context

The underlying event is the highest temperature recorded at London City Airport on 27 June 2026, a date that currently sits at the peak of a three-day provisionally record-breaking heatwave for June in the UK. With 37.3°C reached at Santon Downham in Suffolk on 26 June, the atmosphere is primed for extreme values, yet the crowd-implied probability of 0% for a specific high-temperature range suggests a stark divergence between live weather momentum and market pricing [1].

Historically, London City Airport sees average daily highs above 67°F (25°C) during the warm season, which runs from mid-June to early September, but the current heatwave has pushed local forecasts to 35°C for 26 June and 36°C for 27 June at the airport [2][3]. This contrasts sharply with the 26.6°C recorded at Kew Gardens earlier in 2026 as the year’s hottest day, indicating that the current conditions are significantly more severe than the seasonal baseline [7]. The 0% market probability appears to ignore this escalation, creating a notable gap between analyst consensus on the heatwave’s intensity and the prediction-market odds.

Traders should monitor the Met Office’s hourly updates for London City Airport, particularly the southerly wind flow and falling pressure that are driving temperatures upward, as these are the primary catalysts for further heat [2]. The settlement relies on Wunderground data, so any discrepancy between Met Office forecasts and the station’s actual recorded high will be critical; recent reports confirm the UK has provisionally seen a new maximum temperature record for June for the third consecutive day [1]. No sportsbook lines currently reflect this divergence, leaving the prediction market as the sole venue where this mispricing between live weather data and implied probability can be exploited.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on June 27? on the five venues with material liquidity for prediction markets. Live odds come from the Polymarket Polygon order book — the only source that ships real-time data under an open licence. For Kalshi, Betfair and Manifold we list platform attributes (fee, KYC, settlement, payment) instead of fabricated odds, because their APIs use non-comparable contract definitions.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

FAQ

Where can I trade this market with the lowest fees?

On Best Prediction Markets, 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?

Best Prediction Markets 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 Best Prediction Markets?

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