Highest temperature in London on July 19?

Platform comparison

Market context

London City Airport is expected to record its peak temperature for 19 July 2026 within a specific Celsius range, a real-world outcome that will settle this on-chain weather contract. Today, Polymarket prices the "YES" outcome for any temperature above the current frontrunner at 0%, while the market assigns a 100% probability to the 21°C bracket as the definitive result [1]. This pricing reflects the conditional token mechanics on Polygon, where traders use USDC to lock positions against the specific resolution source from Wunderground, which tracks the highest daily reading for station EGLC [1].

Historical July data for London suggests average highs reach approximately 23°C, with forecasts for July 2026 predicting warm, sunny days and highs between 23°C and 25°C [3]. The current 100% crowd-implied probability for 21°C appears conservative compared to these seasonal norms, yet the market treats this lower threshold as the safe frontrunner, likely due to the specific settlement window ending at 12:00 UTC which may capture morning lows before the afternoon peak [1]. Traders reading this probability should note that while 21°C is the consensus, the meteorological average leans higher, creating a potential divergence between the on-chain price and typical weather patterns.

Key catalysts for this market include the final hourly temperature updates from Wunderground on the settlement day, as the resolution depends strictly on the single highest recorded value for that date [1]. Unlike equity markets driven by earnings, this contract relies entirely on the automated data feed from the London City Airport Station, meaning no human announcements will alter the outcome once the clock starts [1]. Traders monitoring the Polygon chain should watch for liquidity shifts in the 21°C pool as the settlement date approaches, though the current 0% probability for alternative outcomes suggests the market expects the temperature to land squarely in the frontrunner bracket regardless of minor weather fluctuations.

Sources: 1 · 2 · 3

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

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.

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.

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.

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.