Highest temperature in London on May 20?

Platform comparison

Active sub-markets

Market context

The event is the recorded daytime high at London City Airport on 20 May 2026, with settlement tied to the final Wunderground history entry once the day is complete. The present crowd price at 0% for the outcome being referenced as “YES” suggests the market is not treating the relevant temperature band as live uncertainty, which is consistent with the midday timing of the settlement window having already passed. For context, London in May is normally mild rather than hot: climatological highs tend to sit in the mid-to-high teens Celsius, and even recent official observations have shown station-level maxima clustering around 20°C rather than anything extreme. That matters because these markets usually settle on the exact recorded peak at a single station, so a small difference in the Heathrow or city-centre reading can still change the outcome band even when the broader London weather looks similar.

For traders, the key watchpoints are the station-specific final observation, any late data revision on the Wunderground history page, and whether the Met Office or airport reporting feeds show an obvious discrepancy with the forecast archive. There are no live scheduling dependencies beyond the daily observation cycle, but London City Airport’s coastal-influenced position can diverge from central London and from other London stations in a warm spell or an easterly flow. On access, Polymarket’s “no-KYC up to $1,500” typically means small-value participation is available without identity checks, but larger activity can trigger verification, which affects practical accessibility. From a regulatory angle, German GlüStV can make access and marketing sensitive for German users, while US CFTC reach remains relevant because event contracts may still raise US jurisdictional questions depending on user location and product structure.

Sources: 1 · 2 · 3 · 4 · 5

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

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.

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.