Highest temperature in London on July 20?

Platform comparison

Market context

The market tracks the peak temperature recorded at London City Airport on 20 July 2026, with settlement tied to Wunderground’s daily history for station EGLC. Today’s reading of 13°C at the same location offers a stark contrast to the July 20 forecast, yet the current 0% YES probability on the highest-temperature outcome suggests the crowd expects a mild day, likely below 20°C.

Historically, London City Airport rarely exceeds 30°C in mid-July; the last time it hit 32°C was in July 2022 during the UK’s extreme heatwave, while typical highs hover between 22–26°C. The 0% probability aligns with this baseline, as no major heat anomaly has been forecast for 20 July 2026, and the Met Office’s seasonal outlook indicates average summer conditions for southeast England.

Traders should monitor the Met Office’s 24-hour forecast updates and any sudden shifts in the southerly wind flow, which can elevate temperatures if combined with clear skies. A recent Met Office bulletin notes that persistent high pressure over the Atlantic could suppress heat buildup in London this week, reinforcing the crowd’s low-probability stance [2]. Programmatically, this market is best approached by querying Wunderground’s historical API for EGLC and cross-referencing with Met Office model outputs to automate conditional order placement as forecasts evolve.

Sources: 1 · 2

Methodology

We track Highest temperature in London on July 20? 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 Polymarket Bot UK. 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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Polymarket Bot UK trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.