Highest temperature in London on May 23?

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Market context

On 23 May 2026, the highest temperature recorded at London City Airport will determine which range this market settles into. The current 0% probability assigned to the YES outcome reflects the market's interpretation of the resolution criteria: traders are pricing in that no single temperature band will capture the day's peak reading, or that settlement data will prove ambiguous. This disconnect between crowd confidence and the binary structure suggests either extreme certainty about a specific range or genuine uncertainty about how Wunderground's historical data will be finalised for that date.

London's May temperatures typically range between 15°C and 22°C, with historical highs occasionally reaching 26–28°C during warm spells. The Met Office records show that May 2022 saw London reach 27.5°C, whilst May 2020 peaked at 29.2°C. These precedents matter because they establish the plausible upper bound traders should consider; a reading above 30°C would be exceptional but not unprecedented for late spring. The current zero probability suggests the market may be pricing in either a narrow consensus around a specific range or technical friction in how conditional tokens are trading on Polygon.

Traders monitoring this contract should track the UK Met Office's seasonal forecasts released in April 2026, which typically provide confidence intervals for May weather patterns. Additionally, any Atlantic weather systems or high-pressure systems forecast to dominate the south-east during that week will shift expectations materially. The settlement window closes at midday on 23 May, so morning forecasts published by the Met Office or BBC Weather will be the final signals before resolution becomes dependent entirely on Wunderground's historical recording methodology.

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

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.

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.