Highest temperature in London on May 25?

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Active sub-markets

Market context

On 25 May 2026, the highest temperature recorded at London City Airport will settle into one of several defined ranges. The settlement mechanism pulls directly from Weather Underground's historical data for that specific station, converting between Celsius and Fahrenheit via the platform's settings toggle. For traders building automated monitoring systems, the critical dependency is the finalisation timestamp—the market closes at 12:00 UTC, meaning any temperature spike recorded after midday will not affect resolution.

London's May weather patterns show considerable variance year-on-year. The Met Office's 30-year climate normals place the average high for late May around 19–20°C, but extremes matter here. In May 2022, London recorded 28.3°C; in May 2020, highs reached 29.1°C. Conversely, cooler Mays have peaked below 18°C. The 0% crowd probability suggests traders are either pricing in below-average conditions or treating the market as illiquid. Historical precedent indicates May 25 specifically has seen highs ranging from 16°C to 26°C depending on the year, making mid-range outcomes (20–24°C) statistically more probable than extremes.

Traders monitoring this market should track the European Centre for Medium-Range Weather Forecasts (ECMWF) and UK Met Office five-day outlooks as May approaches. Subtropical high-pressure systems tracking northward typically drive May temperature spikes; conversely, Atlantic low-pressure systems suppress them. For programmatic approaches, setting conditional orders tied to forecast model consensus—particularly when multiple models align on temperatures above 23°C—provides an entry mechanism without manual daily checking. The Weather Underground data feed itself updates daily, so automated scrapers can validate forecast accuracy 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

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 PolyGram?

Zero. PolyGram 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.

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.