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 this market's settlement. The contract currently trades at 0% implied probability across all temperature bands, suggesting either extreme confidence in a specific outcome or insufficient liquidity to establish meaningful pricing. Resolution hinges on the Daily Observations table from Weather Underground rather than summary figures, a distinction that matters when intraday peaks diverge from reported highs—a common occurrence at urban airport stations where microclimatic effects influence readings.

Historical August temperatures in London show considerable variation. The Met Office records indicate that August highs typically range between 20–24°C, though extremes have reached 32°C during heatwaves. The August 2022 heatwave pushed readings above 40°C across parts of southern England, though London City Airport itself recorded lower values due to its riverside location and maritime influence. These precedents suggest traders should calibrate expectations around seasonal norms whilst accounting for the possibility of anomalous heat events.

Key variables affecting the 20 August outcome include Atlantic weather patterns, jet stream positioning, and any high-pressure systems establishing over the British Isles in late summer. The UK Met Office issues extended forecasts roughly two weeks ahead, providing early signals of potential heatwaves. Traders monitoring European weather models in early August will gain clearer visibility on whether conditions favour above-average or below-average temperatures. The specific choice of London City Airport—rather than central London or Heathrow—introduces a geographic constraint that typically yields cooler readings than inland sites.

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

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.

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 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.