Highest temperature in London on June 22?

Platform comparison

Active sub-markets

Market context

London City Airport is the settlement point, so the market depends on the highest observed temperature there rather than a city-wide average or a forecast for central London. Polymarket currently prices **27°C** at 81% and **28°C** at 19%, while the crowd-implied probability of **0% YES** on a separate contract line suggests the market is treating the outcome as effectively settled against the relevant threshold or range, not as a broad view on whether London will be warm. BBC Weather’s London City Airport page shows a Monday high of **28°C** and current observations around **13°C**, which is consistent with a warm afternoon but still leaves room for the day’s true peak to land one band above or below the front-runner.[1][3]

For historical framing, late June is firmly within London’s warm season, with WeatherSpark describing the warm period at London City Airport as running from mid-June into early September, and the airport has recorded much hotter June spells in past years, including **33.9°C at Heathrow** on a notable June heat event.[5][6] That matters because the market is not asking whether London will be “hot” in the general sense, but whether the airport’s daily maximum slips into the exact Celsius bucket that wins under the contract’s banding rules. In practice, cross-platform pricing is usually anchored by the same underlying forecast and observation set, so meaningful divergence tends to come from how each venue maps temperature bands rather than from different views of the weather itself.[1][5]

The main catalysts are the final afternoon temperature at London City Airport, any last-minute Met Office forecast adjustments, and how quickly the airport’s observed readings update relative to the settlement cut-off at 12:00 UTC. The Met Office and BBC both carry live London City Airport forecasts, while NOAA’s station feed shows the site’s current observations, so traders are effectively watching the same operational signals that will determine the day’s recorded maximum.[3][4][7][9] If guidance nudges one degree either side of 27°C, the gap between the top two buckets could narrow sharply; if readings stay near the low 30s in surrounding forecasts, the higher band would become more plausible, but the contract still resolves on the station’s measured maximum, not on city-level headlines.[1][3]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on June 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 Best Prediction Markets UK, 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?

Best Prediction Markets UK 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, Best Prediction Markets UK triggers a quick verification flow that finishes in minutes.