Highest temperature in London on July 10?

Platform comparison

Market context

On 10 July 2026, the London City Airport Station will record its peak temperature for the day, a single data point that determines the outcome of a prediction market where the crowd currently assigns zero per cent probability to the “YES” outcome. This implies the market believes the temperature will not fall into the specified range, likely a high bracket such as 40°C or above, which has never been reliably observed at this specific site in recent history.

Historically, July is London’s hottest month, with average highs around 22°C (72°F) at London City Airport, though extreme heatwaves can push temperatures significantly higher[1]. The most notable recent event was the July 2022 heatwave, when parts of the UK recorded 40°C for the first time, though London City Airport itself did not reach that threshold[7][10]. Even during the intense heatwave of July 2025, which affected the British Isles, the airport’s recorded maximum remained below 35°C, suggesting that a 40°C+ reading here is a genuine underdog scenario with minimal historical precedent[10].

Traders should monitor the Met Office’s 7-day forecast for London City Airport, which currently predicts a high of 32°C (89°F) for Friday 10 July with sunny intervals and low rain probability[2][5]. The key catalyst is the arrival of any unexpected southerly airflow, which could elevate temperatures beyond the seasonal norm, but current models show no such anomaly[4]. With the consensus firmly on the “NO” side and no immediate weather warnings indicating extreme heat, the value spot may lie in a contrarian long position only if a sudden, unforecasted heat pulse develops before the settlement window closes on 2026-07-10[3].

Sources: 1 · 2 · 3 · 4 · 5

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

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

FAQ

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.

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.