Highest temperature in London on August 4?

Platform comparison

Market context

London City Airport is expected to set the day’s high for the contract, with late-summer London forecasts clustering around the low-to-mid 20s Celsius rather than extreme heat. Current third-party outlooks put the day’s peak broadly in the **21–27°C** band, with some sources leaning warmer and others cooler: one London forecast shows around **22°C** with light rain risk, while another points to **27°C** and a brief afternoon storm window[3][6]. By comparison, broader August climate guides for London suggest typical daytime highs around **21–22°C**, so the market’s 0% YES price is far below the usual historical range and below even most “warm day” forecasts[8][15][18].

That gap matters because this contract resolves to the **highest** temperature recorded at London City Airport, not the citywide average, and airport readings can run a little higher than a generic London forecast if skies stay clear for long enough. The cross-platform picture is therefore mixed: prediction markets are pricing a near-impossibility at 0%, while weather forecasters still leave open a mid-20s outcome, which would put the settlement in play if the airport station briefly touches the relevant bracket[3][4][12]. A trader should watch the latest Met Office and Wunderground updates for timing of any showers, sea-breeze effects, or convective cloud, because a short-lived afternoon cloudburst could cap the maximum, while prolonged sunshine could lift it towards the upper forecast range[4][12][13].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to PolyGram, which mirrors the Polymarket order book directly.

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

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.