Highest temperature in London on May 25?

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Market context

The market seeks the highest temperature recorded at London City Airport on 25 May 2026. Historical May weather in London typically ranges between 12–20°C, with occasional warm spells pushing into the low-to-mid 20s. The 0% crowd probability suggests traders expect temperatures to fall outside the upper range bins offered, though the specific threshold boundaries determine whether this reflects genuine consensus or simply reflects how the ranges are structured. May 25 falls late in spring, when London's weather patterns transition toward early summer conditions but remain subject to Atlantic weather systems that can suppress temperatures.

London's May temperatures have shown considerable year-to-year variation. The Met Office records indicate that whilst average highs cluster around 18–19°C, outlier years have seen readings exceed 25°C on individual days in late May. The 2022 heatwave pushed May temperatures notably higher across southern England, though such events remain statistically infrequent. Traders should reference historical Wunderground records for London City Airport specifically, as urban microclimates and measurement station placement can produce readings 1–2°C higher or lower than broader regional averages.

The settlement depends entirely on Wunderground's recorded data from the airport station, with the window closing at midday on 25 May 2026. Traders should monitor seasonal forecasts released in April and early May, which typically offer 10–14 day outlooks with reasonable accuracy. High-pressure systems moving across the UK in the days preceding 25 May would be the primary catalyst for elevated temperatures; conversely, Atlantic low-pressure systems would suppress readings toward the historical mean.

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

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

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.

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.

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.

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.