Highest temperature in London on July 21?

Platform comparison

Market context

The market is pricing the highest temperature recorded at London City Airport on 21 July 2026, with settlement based on Wunderground historical data. The 0% implied probability across all temperature ranges suggests either a technical issue with market setup or extreme confidence that no single range will capture the day's peak. London's July climate typically produces highs between 20–25°C, though heat waves can push readings into the high 20s or low 30s. The settlement window closes at midday on the actual date, which creates a timing constraint: if the highest temperature occurs after noon, the market may not capture the full day's range depending on how Wunderground logs data.

Historical July records for London show considerable year-to-year variation. The Met Office records indicate July highs have ranged from 17°C in cooler years to 32°C during heat waves, with the long-term average around 23–24°C. The 2022 heat wave pushed temperatures above 40°C across parts of southern England, though London City Airport recorded lower peaks. Traders should monitor UK Met Office forecasts released in early July 2026 and any heat wave warnings issued by the National Severe Weather Warning Service. Recent climate patterns suggest increasing frequency of above-average July temperatures, though individual day forecasts remain uncertain more than six months ahead. The current zero probability likely reflects market liquidity or range-setting issues rather than genuine consensus about temperature outcomes.

Methodology

This page reviews Highest temperature in London on July 21? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Who Will Win, which mirrors the Polymarket order book at 0% fees.

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.