Highest temperature in London on May 22?

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Market context

London City Airport’s top temperature this afternoon will decide the range, with settlement based on the final Wunderground daily record for 22 May. The market is currently pricing essentially no chance of a high-end outcome, which is plausible given the hour: by early evening UTC, the day’s maximum is often already set unless a late-afternoon burst of sunshine pushes readings a little higher. London’s late-May climatology is usually mild rather than hot, with average highs around the low-20s °C and only occasional spikes into the high-20s.

Comparable London May cases show how quickly expectations can move when the boundary layer clears and winds ease. The Met Office’s live observations for 22 May show mild overnight and early-morning temperatures at central London, while the broader month statistics from WeatherSpark put typical May highs well below heatwave levels. Polymarket’s own related London temperature markets have also shown how tight the distribution can be on the day itself: one recent session resolved firmly in the mid-20s °C, while another leaned towards the upper-20s. That context helps explain why a 0% implied chance is just a snapshot, not a forecast of the final print.

The main catalysts are the afternoon temperature trend, any late cloud cover, and whether a sea breeze reaches the airport site. Traders should watch the final Wunderground history entry for London City Airport once it is finalised, since that is the resolution source rather than a citywide average. With settlement in USDC, the contract is mechanically straightforward once the official daily high is locked, but the path to settlement is still weather-driven rather than crypto-driven; BTC and ETH market moves matter only insofar as they affect broader risk appetite on the platform.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reads Highest temperature in London on May 22? on-chain. Polymarket's quote comes directly from the Polygon order book — the only comparable venue with on-chain settlement. Kalshi (USD, off-chain), Betfair (GBP/EUR, off-chain) and Manifold (play-money) are listed for comparison. Every CTA routes to PolyGram, which mirrors the Polymarket order book directly.

Resolution & payout

Settlement is on-chain via UMA Optimistic Oracle. A proposer posts the outcome with a bond, a two-hour dispute window opens, then the smart contract lifts winning conditional tokens to 1 USDC and sends payments to holders' wallets automatically. No withdrawal fees beyond Polygon gas.

Off-chain venues (Kalshi, Betfair, Smarkets) settle in local fiat through bank-side clearing — faster than SWIFT, slower than on-chain. Manifold pays no real cash.

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.

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.

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.