Highest temperature in London on June 28?

Platform comparison

Market context

On 28 June 2026, the real-world event determining this market is the highest temperature recorded at London City Airport, measured in degrees Celsius. A YES share in this prediction market means you are betting the temperature will fall within the specific range the market defines, while a NO share means you expect it to fall outside that range. Currently, the crowd-implied probability for YES is 0%, suggesting most traders believe the temperature will not reach the target threshold, likely because recent forecasts indicate a high of only 26°C with light rain and moderate breezes[1][7].

Historically, London has seen extreme June heatwaves, with records reaching 35.1°C recently and a historic peak of 40.2°C at Heathrow during a past heatwave[6][9]. However, these outliers are rare compared to typical June days at London City Airport, where average daily highs during the warm season (June to September) sit around 19°C to 21°C, well below the extreme thresholds often used in such markets[3]. The current 0% probability aligns with the pattern that unless a major heatwave is forecast, temperatures rarely breach the upper limits required for a YES outcome, as seen in yesterday’s maximum of 31.1°C which, while high, still fell short of the most extreme ranges[10].

Traders should monitor the Met Office’s heat warnings and any sudden shifts in the southerly wind flow, which can rapidly elevate temperatures. The Met Office recently extended a red extreme heat warning during a previous event, indicating that official forecasts are the primary catalyst for price movement[6]. Since the settlement window ends at 12:00 UTC on 28 June, the final hours of the morning will be critical, and any announcement of a new heat warning before this time could drastically alter the market’s implied probability, though current data suggests conditions remain too mild for a YES result[1][5].

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). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

Resolution & payout

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

FAQ

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

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 Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Prediction Market UK trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.