Highest temperature in London on July 16?

Platform comparison

Market context

London City Airport is set to record its peak temperature for 16 July 2026, with the outcome determining settlement for the weather contract. Current crowd-implied probability for a specific high-temperature threshold sits at 0% YES, yet the broader market on Polymarket shows a clear divergence: 28°C is the frontrunner at 54%, followed by 29°C at 30% [1]. This stark contrast between the binary 0% line and the multi-outcome distribution suggests the binary contract may be mispriced relative to the underlying temperature forecast, a key discrepancy for traders comparing Kalshi and Polymarket odds.

Historical July peaks at London City Airport typically cluster between 25°C and 32°C, making the 0% implied probability for the binary outcome statistically anomalous unless the threshold is set far outside this range. Comparable cases from recent summers show that temperatures exceeding 28°C occur with notable frequency, supporting the Polymarket consensus that 28°C is the most likely outcome [1]. The 0% line on the binary market appears to ignore this established thermal baseline, creating an arbitrage opportunity when viewed against the multi-outcome probability distribution.

Traders should monitor real-time meteorological updates from BBC Weather, which currently reports 13°C with southerly winds and 88% humidity at 3 PM UTC [2]. While today’s conditions are cool, the settlement window closes at 12:00 UTC on 16 July 2026, meaning the final reading depends on afternoon heating trends. No specific weather announcements are scheduled, but the primary catalyst is the hourly temperature progression from Wunderground, the designated resolution source [1]. Divergence between the binary 0% and the 54% probability for 28°C remains the critical signal for cross-platform analysis.

Sources: 1 · 2

Methodology

We track Highest temperature in London on July 16? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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.

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.

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.