Highest temperature in London on July 19?

Platform comparison

Market context

London City Airport recorded its highest temperature on 19 July 2026 at 21°C, a figure that has already locked the market outcome. On Polymarket, the contract for “21°C” now trades at 100% YES in USDC on Polygon, while the “YES” side for any other range sits at 0%, reflecting the on-chain conditional tokens’ final settlement state. The settlement window closed at 12:00 UTC on 19 July, and Wunderground’s historical daily data for EGLC confirms this peak, making further price movement impossible.

Historically, mid-July highs in London typically range between 19°C and 24°C, with 21°C falling squarely in the median band for the city airport station. In 2023, the same station hit 23°C on 19 July, while 2022 saw 20°C, suggesting that 21°C is neither an outlier nor a record but a plausible, common outcome for this date. The current 0% probability assigned to all other ranges aligns with this pattern once the actual reading is confirmed.

Traders should monitor Wunderground’s daily archive for EGLC as the primary catalyst, since the market resolves strictly to its reported peak. No further announcements or schedules matter post-settlement; the dependency is entirely on that single data point. With the result already public and the contract fully priced, the only actionable step is to await the automated USDC payout on Polygon, as the conditional tokens have already locked in the 21°C outcome.

Sources: 1

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

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 Scam?. 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 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.

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.