Highest temperature in London on May 25?

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Market context

London's weather on 25 May 2026 will determine whether the day's peak temperature at City Airport exceeds specific thresholds. Late May typically sits at the cusp of spring-to-summer transition in the UK capital, with average highs around 20°C and occasional warm spells pushing into the mid-20s. The 0% crowd probability suggests traders are pricing in either extreme confidence in cooler conditions or minimal liquidity and engagement on this particular date.

Historical May records for London show considerable variability. The Met Office data indicates that whilst temperatures in the low-to-mid 20s are routine for late May, readings above 25°C occur roughly once every two to three years during this period. The highest May temperature ever recorded in London stands at 29.4°C (1944), though such extremes remain statistical outliers. Seasonal patterns favour moderate warmth rather than heat waves this early in the calendar year.

The resolution hinges entirely on Wunderground's historical records from London City Airport Station, which captures actual observed conditions rather than forecasts. Traders should monitor UK Met Office five-day forecasts as the date approaches—typically issued with increasing precision from mid-May onwards. Atmospheric pressure systems, jet stream positioning, and any early high-pressure ridges moving northward from continental Europe would be the primary catalysts for materially warmer outcomes. Current seasonal models suggest near-normal conditions for late May 2026, consistent with the market's current pricing.

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

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

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.

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.