Highest temperature in London on July 5?

Platform comparison

Market context

London City Airport is set to record its highest temperature for 5 July 2026, with the market currently pricing a 0% chance of any outcome resolving as a specific high-temperature threshold. On-chain, USDC liquidity on Polygon backs conditional tokens that will settle once Wunderground publishes the day’s peak Celsius reading for the EGLC station. The contract’s frontrunner is 29°C at 47%, while 28°C holds 44%, indicating the crowd expects a warm but not extreme day despite the zero probability on the YES side of the binary framing.

Historically, London’s July highs rarely exceed 35°C, with the all-time record of 40.2°C set at Heathrow on 19 July 2022, not at City Airport [3]. Comparable early-July readings at EGLC typically range 26–30°C under settled conditions, aligning with the Met Office’s forecast of 29–31°C daytime highs for 5 July under mostly settled weather [2]. The current 0% YES probability likely reflects a binary mispricing or a specific threshold set above plausible outcomes, rather than a belief that no high temperature will occur.

Traders should monitor the Met Office’s 4 July forecast update and real-time Wunderground data for EGLC, as rain bands and gusty winds forecast for 4–5 July could suppress temperatures to 15–19°C if the wet pattern persists [5]. The settlement hinges entirely on Wunderground’s official daily high for EGLC, with no alternative sources accepted. Any shift from the predicted 29–31°C range to the cooler 15–20°C range cited in weather alerts would invalidate the 29°C frontrunner and reshape liquidity across the temperature bins [5].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

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

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 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.

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 Legit? trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.

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.