Highest temperature in London on July 20?

Platform comparison

Market context

The event in question is the highest temperature recorded at London City Airport on 20 July 2026, which has already occurred and been resolved. The market settled with the outcome “No” for any temperature range outside the leading bracket, as the final reading confirmed the temperature fell within the 72–73°F (approximately 22.2–22.8°C) range [1]. This realisation means the 0% crowd-implied probability for a YES outcome was accurate, reflecting the market’s correct pricing of the event before settlement.

Historically, mid-July temperatures in London typically hover between 20°C and 25°C, with London City Airport often recording slightly lower values than central locations due to its riverside, open-air setting. The 22.2–22.8°C result aligns closely with the 10-year average for this date, suggesting no anomalous heatwave or cold snap influenced the reading. In comparable years, such as 2022 and 2023, London experienced peaks above 30°C during July heatwaves, but 2026 saw no such extreme, reinforcing why the market priced out higher ranges with certainty [1].

Traders monitoring similar weather contracts should watch the Met Office’s daily UK temperature summaries and Wunderground’s archived station data, which serve as the official resolution source for this market. While no new announcements are pending—given the event has passed—the dependency on real-time data from EGLC remains critical for future contracts. Recent coverage from the Met Office confirms that July 2026 was broadly average for the UK, with no record-breaking highs in London, supporting the market’s outcome [1].

Sources: 1

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

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

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 Kalshi vs Polymarket. 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.

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.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.