Highest temperature in London on July 4?

Platform comparison

Market context

On 4 July 2026, London City Airport will face its peak summer heat, with the market betting on whether temperatures breach a specific Celsius threshold. The crowd-implied probability sits at 0% for the "YES" outcome, reflecting a consensus that extreme heat is unlikely at this coastal, urban station. Historically, July is London’s hottest month, averaging a high of 22°C (72°F), yet the city’s record of 40.2°C was set inland at Heathrow during the 2022 heatwave, not at EGLC [6]. London City Airport, situated near the Thames with lower elevation and higher humidity, typically records temperatures 1–2°C below inland sites, making a 40°C spike here a statistical underdog scenario [2][7].

Traders should monitor the Met Office’s daily forecasts for the third week of July, as UK heatwaves often arrive via southerly flows that intensify inland first before reaching the airport [4]. A recent evaluation of the July 2025 heatwave noted that while brief, intense spikes affected all British Isles areas, EGLC consistently lagged behind Heathrow in peak readings [10]. The key catalyst is the arrival of a high-pressure system from the continent; if one materialises, the airport’s maritime exposure may cap temperatures below the threshold, preserving the 0% value spot. Contrarian angles might only emerge if a rare, stagnant high-pressure dome traps heat directly over the city, but current data suggests EGLC remains the favourite for staying cool [1][3].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on July 4? 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 Who Will Win. 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.

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.