Highest temperature in London on August 5?

Platform comparison

Market context

London starts the day with forecasts clustered around the mid-20s Celsius, and the latest market pricing is split between **25°C** and **26°C** rather than pointing to a clear outlier. Recent short-range guidance also leans to a warm but not extreme day, with Met Office commentary cited in market data pointing to high pressure and southerly warm-air advection, while ensemble spread remains narrow at about 24–26°C depending on cloud and the timing of any weak frontal passage.[1]

That setup matters because August in London often produces maxima in the low-to-mid 20s rather than very hot extremes, so a 0% implied chance on the market’s more distant bands is broadly consistent with the seasonality and with the absence of a strong heat signal in the near-term outlook.[2][11][14] For context, London’s hottest days can jump well beyond 30°C in stronger continental setups, but the current forecast and recent local reporting point to a milder warm spell, with 25°C the most commonly advertised high for the day and no sign of a severe heat event.[3][15][16]

Traders should watch for any update in the morning forecast from the Met Office and for changes in cloud cover, shower timing or wind direction, because those are the main variables that can pull a London maximum one band lower or higher on a day like this.[1][3] The market resolves to the highest temperature at London City Airport Station on the day, so late-afternoon warmth or an early peak before marine cloud arrives can matter more than the headline daytime high, especially if the day ends up sitting close to the 25°C/26°C boundary.[1]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on August 5? 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

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

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.

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.

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.