Pronóstico: Highest temperature in London on July 21?

Platform comparison

Market context

The market is pricing a 1% chance that London's highest temperature on 21 July 2026 will exceed 40°C, based on readings from London City Airport Station. Polymarket traders are currently holding YES tokens at a steep discount, reflecting extreme scepticism about such heat. The conditional token structure means buyers of YES are betting against the baseline expectation embedded in the USDC-denominated order book on Polygon.

London's recorded temperature extremes provide the historical anchor. The UK's all-time high of 40.3°C occurred in July 2022 at Coningsby, Lincolnshire, whilst London itself has never officially recorded 40°C at any station. The City Airport site, located in East London, typically registers slightly cooler readings than central London due to proximity to the Thames estuary. July 2022 saw multiple days above 35°C across the capital, but sustained heat of that magnitude remains rare; the 1% probability reflects how infrequently such thresholds are breached at this specific location.

Traders monitoring this contract should track the Met Office's seasonal forecasts and any atmospheric patterns emerging in early July 2026. Persistent high-pressure systems over the UK, particularly those anchored for multiple consecutive days, would be the primary catalyst shifting probability. European heat waves occasionally extend northward into British airspace, though the Atlantic's moderating influence typically prevents sustained extreme heat. Real-time weather data from early July will matter far more than current pricing; the market's current odds reflect baseline climatology rather than any specific forecast signal.

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

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

FAQ

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

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.