Highest temperature in London on August 3?

Platform comparison

Market context

London’s **highest temperature** on 3 August will be set by the peak reading at London City Airport Station, so the contract is really a single-day intraday weather bet rather than a general “London temperature” view. The current crowd price at **0% YES** is a clear outlier against the market framing, because live pricing in comparable temperature markets usually concentrates around the most likely range rather than implying a zero-probability outcome; Polymarket’s own comparable contract for the same event shows the front of the book sitting around **30–31°C** rather than anywhere near a flat-line dismissal.[4] Recent London heat coverage also shows how quickly forecasts can move the upper bound: BBC reporting and Met Office commentary this summer have already tied the capital to its warmest day of the year and multiple heat alerts, with temperatures reaching **26.6°C** at Kew Gardens in one recent spell and official warnings issued for south-east England.[2][12][13]

For traders, the key catalysts are the day-ahead and morning forecast updates, any Met Office warning changes, and whether the local synoptic setup supports full sun and light winds, which would favour a higher maximum before the settlement window closes at 12:00 UTC. The market’s reference point is the Wunderground daily history page for London City Airport, so late revisions to the station record matter more than headline city forecasts, and the contract will not settle until the day’s data are complete.[1] On the comparable-contract side, if sportsbook or other venue pricing is available, the main check is whether those lines cluster around the low 30s Celsius or diverge sharply; with Polymarket already implying a warm day, any meaningful gap versus a 0% YES read would point to either stale pricing or a misread of the settlement rule.[4]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in London on August 3? 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 Kalshi vs Polymarket, 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

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 Kalshi vs Polymarket. 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.

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.