Highest temperature in London on August 11?

Platform comparison

Market context

On 11 August 2026, the highest temperature recorded at London City Airport will fall into one of several defined ranges. The market resolves using the Daily Observations table from Weather Underground rather than the summary Day High & Low figure—a distinction that matters when intraday readings spike above the official daily maximum or when station equipment logs granular measurements that don't appear in headline figures. For programmatic traders, this means building a data pipeline that queries Wunderground's raw observation feed directly, not relying on API endpoints that surface only the cleaned daily summary.

August temperatures at London City Airport typically peak between 20–25°C, with occasional excursions into the 26–28°C band during heat waves. Historical August records show the station rarely exceeds 30°C; the 0% crowd probability suggests the market is pricing in either a narrow range resolution or confidence that August 2026 will track seasonal norms. Comparable years—such as August 2022, when London experienced sustained temperatures above 30°C during an exceptional heat event—demonstrate that whilst extreme readings are rare, they do occur and can shift market odds sharply once weather models converge on a forecast.

Traders should monitor the UK Met Office's extended forecast from mid-July onwards and track Atlantic pressure patterns that drive warm continental air into southern England. Jet stream positioning in early August will signal whether blocking high pressure systems develop; such systems are the primary catalyst for temperatures exceeding 25°C at the airport. Real-time observation feeds should be queried from 06:00 UTC on resolution day through the 12:00 settlement window to capture the full daily range before markets close.

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

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

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.

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 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.