Highest temperature in London on August 20?

Platform comparison

Market context

On 20 August 2026, the highest temperature recorded at London City Airport will determine which temperature band this market resolves to, with settlement occurring at midday UTC. The resolution methodology specifies the Daily Observations table on Weather Underground as the authoritative source, distinguishing it from summary high-low figures that may occasionally diverge. The 0% crowd-implied probability suggests traders currently assign negligible likelihood to the upper temperature ranges offered, though the specific bands available are not detailed in the market specification.

August temperatures at London City Airport typically range between 18°C and 25°C, with historical August highs rarely exceeding 28°C. The station's 30-year average for mid-August sits around 22°C. Extreme heat events above 30°C occur infrequently in London, with the most recent occurrence in July 2022 when temperatures reached 40.3°C nationally. The current zero probability reading suggests the market may be pricing in either a very narrow upper band or reflects limited trader engagement on this specific contract.

Traders monitoring this market should track the UK Met Office's seasonal forecasts and any significant atmospheric patterns emerging in summer 2026. The European summer weather pattern—particularly the position of the jet stream and any high-pressure systems over the continent—will be the primary driver of temperature outcomes. Cross-platform comparison data between Polymarket and Kalshi offerings on this contract would reveal whether probability divergence reflects genuine disagreement on meteorological likelihood or simply differences in liquidity and trader participation between platforms.

Methodology

This page reviews Highest temperature in London on August 20? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to PolyGram, which mirrors the Polymarket order book at 0% fees.

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.

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.