Highest temperature in London on August 7?

Platform comparison

Market context

London’s daytime high is the key variable, and the market is effectively pricing where the thermometer peaks at London City Airport before the settlement cut-off. The crowd has made **25°C** the favourite at **30%**, with **26°C** close behind at **29%**, while the market as a whole is still assigning only **0%** to a different outcome at the moment, so the book is concentrated around a fairly mild late-summer range rather than a spike. [2]

That makes the current **favourite** the mid-20s band, with the **underdog/value** question sitting in whether the top of the distribution is being underpriced if London turns a touch hotter than expected. Comparable August norms lean cooler than the current frontrunner: long-run London August daytime averages are around **22°C**[10], while a recent forecast for Friday 7 August 2026 pointed to **26°C** with a low rain risk[4]. Recent UK heat reporting also matters because a broader warm spell can push London a degree or two above model consensus, but the market still looks anchored to a fairly standard summer day rather than an extreme outlier[11][12].

The main catalysts are short-range forecast updates, cloud cover, and whether any warm advection from the wider UK heat pattern reaches inner London by early afternoon, because the market settles on the **highest recorded temperature** in the Weather Underground daily observations table, not the summary high/low line. Traders should watch late-breaking Met Office and local forecast revisions, but the settlement source makes the decisive factor the station’s observed peak rather than what headline forecasts suggested earlier in the day[15].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on August 7? 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

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

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 Who Will Win 2026. 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 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.