Highest temperature in London on May 27?

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Market context

The highest temperature recorded at London City Airport on 27 May 2026 will determine the settlement outcome for this market. The resolution uses historical weather data from Weather Underground, capturing the peak daily temperature in Celsius across all daylight and evening hours at that specific monitoring station in East London.

London's late May temperatures typically range between 18–22°C, though the city has recorded highs exceeding 25°C during warm spells in this period. The 0% crowd probability suggests traders expect conditions below the lowest available range threshold on the market. Historical May data from City Airport shows that temperatures above 20°C occur in roughly 60–70% of years, whilst days exceeding 25°C are less frequent but not exceptional. The 2022 heatwave pushed May temperatures into the high 20s across southern England, demonstrating that outlier conditions do materialise.

Traders should monitor the Atlantic pressure systems and jet stream positioning in early May 2026, which determine whether continental warm air reaches the UK or Atlantic systems deliver cooler conditions. The Met Office's extended forecast, typically issued three weeks ahead, will provide initial guidance on the probability of anomalously warm conditions. Seasonal patterns favour mild rather than hot conditions in late May, though any blocking high-pressure system over northern Europe in the preceding weeks would shift probabilities substantially upwards. Weather forecasting confidence remains limited beyond ten days, making early-month atmospheric signals the primary catalyst for significant probability shifts.

Methodology

This page is a comparison snapshot: one live quote (Polymarket), four reference venues with their key attributes, and a single execution path — every trade button routes to Sport Prediction, which mirrors the Polymarket order book directly.

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 Sport 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?

Sport 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.

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.

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.