Highest temperature in London on May 22?

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Active sub-markets

Market context

London’s maximum on 22 May is measured at London City Airport, and the market settles on the temperature band containing the day’s highest recorded reading once Wunderground finalises the data. With the noon settlement window already past, the live question is whether a late-afternoon spike can move the reading out of the lower bands. London’s late-May climatology is usually mild rather than hot, with average highs around the low-to-mid 20s Celsius, but short-lived warm spells can still push the city well above seasonal norms when sunshine and light winds line up.

For context, Polymarket’s own nearby temperature markets have been heavily concentrated in a single outcome close to resolution, including 24°C being fully priced for 21 May and 28°C dominating the 22 May market earlier in the day. Longer-run London history shows that extreme May heat is possible but uncommon: the city’s May record maximum is 32.8°C, set in 1922, while recent standout warmth has tended to be episodic rather than persistent. That is why a market implying 0% for the upper bands is best read as a reflection of current weather conditions, not a statement that higher readings are impossible.

Traders should watch the afternoon observation pattern at London City Airport, final Met Office and Wunderground updates, and any shift in cloud cover or wind that could cap the peak earlier than expected. No major scheduled announcement normally drives a temperature market, so the key dependency is the day’s realised weather rather than a policy or data release. On access, the regulatory frame matters: German GlüStV treatment can limit or prohibit use from Germany depending on platform status, the US CFTC reach is relevant because event contracts can fall within US commodities oversight, and “no-KYC up to $1,500” means smaller balances may be usable with lighter identity checks, which can make the market more accessible but does not remove jurisdictional restrictions or tax reporting obligations.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on May 22? on the five venues with material liquidity for prediction markets. Live odds come from the Polymarket Polygon order book — the only source that ships real-time data under an open licence. For Kalshi, Betfair and Manifold we list platform attributes (fee, KYC, settlement, payment) instead of fabricated odds, because their APIs use non-comparable contract definitions.

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 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.

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 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.