Highest temperature in London on August 4?

Platform comparison

Market context

London’s warm spell has eased into a more typical early-August setup, with recent forecasts pointing to highs around the low-to-mid 20s Celsius rather than the extreme 30C+ values seen earlier in the week. One current London forecast puts today near 28°C, while other outlooks for the city and south-east suggest around 21–23°C, with the possibility of cloud and light showers rather than prolonged heat.[4][13][15]

That is important because the market settles on the highest temperature recorded at London City Airport Station before midday UTC, so only the warmest part of the morning and late morning window matters. London’s August climate usually sits around 22°C by day, with some rain in the month, which makes a 0% yes-price understandable only if traders believe today will stay below the relevant range or that the forecast heat will peak after the settlement cut-off.[1][8][16]

For traders, the key catalysts are any last-minute shifts in the forecast track: a stronger-than-expected sunny spell, any morning cloud break, or a rain band that suppresses the daytime maximum. The most relevant signals are the latest local London forecast updates and airport-observed conditions; if the warmer end of current guidance holds, the market can still move quickly even from a low starting probability.[6][17]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on August 4? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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 Prediction Today. 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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Prediction Today trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.