Highest temperature in London on May 28?

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Market context

On 28 May 2026, London City Airport's weather station will record a daily high temperature in Celsius, with traders on Polymarket currently pricing all temperature ranges at zero probability across the board. This settlement mechanism relies on historical data pulled from Weather Underground's London City Airport archive, making the contract's outcome entirely dependent on actual meteorological conditions recorded that specific day rather than forecasts or modelled estimates.

May temperatures at London City Airport typically range between 15°C and 22°C based on thirty-year climate normals, though the station has recorded highs exceeding 25°C during warm springs. The 0% crowd probability suggests either insufficient liquidity in the market or genuine uncertainty about whether any outcome will materialise—a common pattern for weather contracts settled months in advance where traders hesitate to commit capital without near-term forecast data. Historical precedent shows May can deliver variable conditions; the UK experienced a notably warm May 2022 with several days above 25°C, whilst May 2023 remained cooler and wetter across southern England.

Traders monitoring this contract should track the Met Office's seasonal outlooks released in April 2026, which typically provide confidence intervals for temperature anomalies across the UK. The actual settlement hinges entirely on Weather Underground's historical records for that single day—no adjustments for methodology changes or station relocations apply once the market enters its resolution window on 28 May at 12:00 UTC. Any technical issues with the Weather Underground archive during that window could delay resolution, though Polymarket's conditional token structure on Polygon means positions remain tradeable throughout any settlement delays.

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

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 Kalshi UK, 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?

Kalshi UK 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.

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.

Do I need to KYC for this market?

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