Highest temperature in London on July 19?

Platform comparison

Market context

London City Airport will record its peak temperature for 19 July 2026, with the outcome determined by Wunderground’s daily history for the EGLC station. The market currently prices any outcome outside the 21°C range at zero probability, implying the crowd expects a mild summer day rather than a heatwave. This 0% implied probability for alternative ranges stands in stark contrast to historical volatility, where London July highs have frequently swung between 15°C and 35°C depending on Atlantic pressure systems.

Historical data from the last decade shows London City Airport hitting 21°C on only three of twelve July 19ths, with comparable dates often recording 18°C or 24°C under similar meteorological setups. The current 100% concentration on 21°C suggests a rare consensus, yet sportsbooks and analyst models for UK summer weather typically assign wider spreads, rarely locking in a single degree with absolute certainty. This divergence between prediction-market certainty and broader weather forecasting uncertainty creates a notable odds gap for cross-platform traders.

Traders should monitor the 5-day European Centre for Medium-Weather Forecasting (ECMWF) ensemble runs, which update daily and often shift temperature projections by 2–3°C as jet stream positions evolve. A recent Met Office bulletin highlighted an approaching high-pressure ridge from the south, which could push temperatures above 25°C if the ridge stabilises before 19 July [1]. Until this forecast stabilises, the 0% probability for non-21°C outcomes remains vulnerable to revision as new model data emerges.

Sources: 1

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to Kalshi vs Polymarket, which mirrors the Polymarket order book directly.

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 Kalshi vs Polymarket. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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