Highest temperature in London on May 23?

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Market context

On 23 May 2026, London City Airport's weather station will record a daily maximum temperature in Celsius. Polymarket currently prices all temperature ranges at zero, reflecting either sparse liquidity or genuine uncertainty about which bracket will resolve. The settlement hinges on Wunderground's historical data feed for that specific date and location, with the window closing at midday UTC.

London's May temperatures typically range between 15–22°C, though the city has recorded highs of 27–28°C during warm spells in late May over the past decade. The 2022 heatwave saw temperatures exceed 30°C in parts of the South East, but such extremes remain uncommon for this time of year. City Airport, situated in Newham on the Thames, tends to register slightly cooler readings than central London due to its proximity to water and lower urban heat island effect. Historical May data from the same station provides the most reliable baseline for assessing probability distributions across the available ranges.

Traders should monitor the Met Office's seasonal outlook for spring 2026 and any Atlantic weather patterns that develop in April and early May. High-pressure systems drifting north from the continent can drive temperatures upward, whilst unsettled Atlantic fronts typically suppress maxima. The UK's weather forecasting community typically gains confidence in 10–14 day outlooks around early May, which will be the last opportunity to assess whether anomalous warmth or coolness is likely. No specific announcements or scheduled events directly influence this market; it remains a pure weather-dependent contract.

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 PolyGram, which mirrors the Polymarket order book directly.

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.

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.