Highest temperature in London on May 31?

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Market context

On 31 May 2026, the highest temperature recorded at London City Airport will fall into one of several defined ranges. The market currently shows 0% implied probability across all temperature brackets, suggesting either extreme uncertainty or insufficient trader participation at this early stage. Settlement depends on historical weather data from Wunderground, with the measurement window closing at noon UTC on the specified date.

London's late May temperatures typically cluster between 18°C and 24°C, based on thirty-year averages. The city has recorded highs above 28°C on 31 May in recent decades, though such outcomes remain statistically uncommon. The 2022 heatwave pushed late-May readings into the low 30s across southern England, establishing that extreme scenarios are plausible if atmospheric conditions align. Traders should calibrate expectations against both seasonal norms and the increasing frequency of above-average May temperatures observed since 2015.

The primary catalyst affecting this market is the Met Office's seasonal outlook, typically published in April 2026, which will signal whether high-pressure systems or cooler Atlantic patterns are forecast for late May. Any significant weather warnings issued in the week preceding 31 May could shift trader positioning materially. Current cross-platform comparison shows negligible trading activity on competing platforms, indicating this remains a niche contract with limited liquidity and wide spreads. Early traders entering positions should account for the extended settlement window and potential for late-stage volatility as the date approaches.

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?

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.

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.