Highest temperature in London on May 31?

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Market context

The highest temperature recorded at London City Airport on 31 May 2026 will determine which temperature band resolves as correct. Historical May data for the London area shows that end-of-month temperatures typically range between 18–24°C, with occasional warm spells pushing into the mid-to-high 20s. The 0% crowd probability suggests traders are pricing in either extreme caution or uncertainty about the specific resolution mechanics, though late May in London rarely produces exceptional heat. Comparable years show that temperatures exceeding 28°C on 31 May are uncommon but not unprecedented; the Met Office records indicate that May heat waves, when they occur, tend to cluster in the earlier weeks of the month rather than the final days.

The key variable affecting May 31 temperatures will be Atlantic weather systems and any high-pressure systems establishing themselves over the British Isles in the preceding weeks. Late May typically sits at the transition point between spring and early summer patterns, making forecasts beyond two weeks increasingly unreliable. Traders should monitor seasonal outlooks from the Met Office from mid-May onwards, as these will provide the most credible guidance on whether anomalous warmth is likely. The settlement window closes at noon on 31 May, meaning the highest temperature recorded up to that point—rather than the full day's peak—will determine the outcome. Any unusual atmospheric blocking patterns developing in late April or early May would be the primary catalyst shifting probabilities away from the current consensus.

Methodology

We track Highest temperature in London on May 31? 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

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

Where can I trade this market with the lowest fees?

On Champions League Prediction, 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?

Champions League Prediction 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.

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.

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?

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