Highest temperature in London on July 21?

Platform comparison

Market context

On 21 July 2026, the highest temperature recorded at London City Airport will fall into one of several defined ranges, with settlement determined by Wunderground's historical weather data for that specific station. The current Polymarket pricing reflects zero probability across all temperature brackets, a technical artefact common when markets first launch and liquidity pools await initial traders to establish conditional token valuations on Polygon. USDC deposits will determine position sizes, with the eventual payout structure dividing the pool among holders of whichever temperature-range token resolves as correct.

London's July temperatures have historically clustered between 20–26°C, with the City Airport station recording a July maximum of 28.4°C in 2022 and 27.1°C in 2023. The 2022 heatwave that drove UK temperatures above 40°C affected inland stations more severely than the riverside airport location, which benefits from thermal moderation. Comparable July days at this station rarely exceed 29°C; traders should anchor expectations around the 22–27°C range as the most probable outcome based on recent climatology.

The UK Met Office publishes extended forecasts from mid-July onwards, typically releasing 10-day outlooks by early July 2026. Traders monitoring atmospheric pressure patterns and jet-stream positioning in the weeks preceding settlement will have the clearest signal for whether high-pressure systems or Atlantic weather systems dominate that week. Any significant heatwave warnings issued by the Met Office in the days before 21 July would shift probability markedly toward higher temperature brackets, whilst unsettled conditions would favour cooler ranges.

Methodology

We track Highest temperature in London on July 21? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is PolyGram. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

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.