Highest temperature in London on July 13?

Platform comparison

Market context

London City Airport is forecast to reach a high of 27°C today, 13 July 2026, with sunny conditions and a moderate southerly breeze, making the current 5% YES probability on the “highest temperature” contract appear conservative relative to today’s actual reading [7]. The market resolves to the Celsius range containing the peak temperature recorded at EGLC on this date, settled via Wunderground’s daily history for the station, with settlement closing at 12:00 UTC on 2026-07-13.

Historically, July 13 at London Heathrow—the closest major benchmark—has seen a record high of 31.4°C in 1983, while the UK’s absolute record of 40.2°C occurred at Heathrow in 2022, and a July-specific record of 36.7°C was also logged there in 2015 [2][3][5]. London City Airport typically records slightly lower peaks than Heathrow due to its coastal Newham location, but recent heatwaves have pushed May–July highs above 35°C across the capital for the first time in UK records, suggesting the 5% implied chance of a higher-than-expected spike may underprice extreme outlier scenarios [6].

Traders should monitor real-time Wunderground updates for EGLC as the settlement window closes within hours, alongside Met Office heatwave advisories that could signal rapid temperature shifts before 12:00 UTC [6]. The contract trades on Polygon using USDC, with conditional tokens enabling on-chain position sizing; since resolution is time-bound and data-driven, latency in Wunderground’s daily update could create brief arbitrage opportunities if the reported peak diverges from live sensor feeds [7][9].

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'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.

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