Highest temperature in London on May 25?

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Market context

On 25 May 2026, the highest temperature recorded at London City Airport will determine which range this market resolves to. The settlement window closes at midday, capturing the peak temperature for the full calendar day as measured by Wunderground's historical data feed from that station.

London's May temperatures typically range between 15–22°C, with the long-term average high around 19–20°C. Exceptional heat days—those reaching 25°C or above—occur roughly once every three to five years during May in the capital. The 0% crowd-implied probability reflects baseline expectations that late May will track within normal seasonal bounds rather than spike into anomalous warmth. Historical precedent suggests traders should calibrate against May's typical variance: whilst 28–30°C days are rare, they remain meteorologically plausible under high-pressure systems that occasionally drift northward from continental Europe during late spring.

Traders monitoring this contract should track the UK Met Office's extended outlook for late May 2026 and any emerging Atlantic weather patterns that might drive warm air masses into the British Isles. Jet stream positioning in the weeks preceding the settlement date will signal whether blocking anticyclones could establish themselves over the region. The 0% reading indicates the market currently assigns negligible probability to any temperature bracket above baseline expectations, leaving potential value if seasonal forecasts shift toward warmer-than-average conditions as May approaches.

Methodology

This page reviews Highest temperature in London on May 25? across five venues. We show live odds for Polymarket-based markets (sourced from the Polygon order book); for other venues we list platform attributes, since the comparable contracts are not exposed via a public API on every venue. Every CTA points at PolyGram — the application we operate, where you trade directly against the Polymarket order book at 0% fees.

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 PolyGram, 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?

PolyGram 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.

Do I need to KYC for this market?

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