Highest temperature in London on July 21?

Platform comparison

Market context

On 21 July 2026, the highest temperature recorded at London City Airport will fall into one of several defined ranges, with settlement determined by Wunderground's historical weather data for that specific station. The current market pricing reflects zero probability across all temperature bands, a technical artefact of how Polymarket's conditional token architecture initialises contracts before meaningful trading volume establishes price discovery. USDC liquidity on Polygon will accumulate as the settlement date approaches and traders begin positioning for summer weather outcomes.

London's July temperatures have historically clustered between 20–26°C at City Airport, though the station has recorded extremes ranging from 13°C to 32°C across the month since records began. The 2022 heatwave pushed readings to 40°C across southern England, though City Airport's riverside location and urban heat-sink effects typically moderate peaks relative to inland sites. Traders should reference the Met Office's seasonal forecasts and any anomalous Atlantic weather patterns emerging in early July 2026, as these shape the probability distribution across temperature bands weeks before settlement.

The key catalyst remains the North Atlantic Oscillation and jet stream positioning in mid-summer 2026. High-pressure systems anchored over the British Isles drive temperatures upward; conversely, Atlantic low-pressure systems and northerly flow suppress peaks. Traders monitoring European weather models from early July onwards will gain signal on whether the market should price toward the 20–23°C range (typical cool summers) or higher bands (heatwave scenarios). The settlement window closes at 12:00 UTC on 21 July, locking in whatever maximum Wunderground records for that calendar day.

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