Highest temperature in London on July 24?

Platform comparison

Market context

Polymarket is pricing this London temperature contract at **0% YES** for every outcome other than the current front-runner, so the book is effectively assuming the day’s peak at London City Airport will stay in the lowest relevant bands rather than spike into a hotter bucket. On Polymarket, traders are buying and selling **conditional tokens** settled in **USDC** on **Polygon**, so the market price is the crowd’s live estimate of where the verified Wunderground reading will land, not a forecast of the city’s average weather.

That 0% reading sits against a seasonal backdrop in which July is typically London’s warmest month, with average highs around the low 20s Celsius, but short-lived heatwaves can push readings materially higher. Recent July coverage has already shown the capital moving well above normal, with the Met Office cited in reporting as putting London at 34C and warning of highs in the low 30s during the same week, which is the kind of pattern traders use to judge whether the distribution is skewed towards an upside surprise or a more ordinary summer outcome.[1][3][6]

For this market, the practical catalysts are straightforward: the final Wunderground entry for London City Airport, any late-day convective showers or marine breezes that cap the maximum, and the usual post-midnight update cycle before resolution at 12:00 UTC. Because settlement depends on the **highest recorded temperature** at that station rather than a forecast point, traders will usually watch airport observations and nearby Met Office updates rather than broad London city forecasts; any surprise surge in the early afternoon matters far more than the evening cool-down.

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

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 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.