Highest temperature in London on August 4?

Platform comparison

Market context

London City Airport’s top reading on 4 August will almost certainly be set by the day’s warmest afternoon hour, with the current market pricing at **0% YES** implying the crowd sees essentially no path to an outlier hot day. The base-rate picture is ordinary summer warmth rather than heatwave territory: long-run London August daytime maxima are around 22°C, and current August forecasts for London cluster in the low-20s with some rain or cloud rather than sustained extreme heat.[2][9][1] That makes the favourite side the **NO** by a wide margin, with the only real upside for YES coming from a sharper-than-expected afternoon spike if cloud breaks more than forecast.

Recent forecast sets point to a fairly narrow band around the low-to-mid 20s, which is exactly where value hunters tend to look when the market has gone to zero. AccuWeather’s August view has London daily highs between 67°F and 78°F, while other August forecasts show 4 August around 22°C with overcast or drizzle and neighbouring days only a degree or two either side.[3][2] Historically, 4 August in England has often produced highs in the low-to-mid 20s, with occasional readings closer to 25–26°C but not consistently beyond that.[1] On that framing, a contrarian YES needs a genuine warm-break scenario; otherwise the consensus sits comfortably on a middling summer high rather than a threshold-breaking heat event.

For traders, the main catalysts are the short-range forecast updates through the morning and early afternoon, plus any sign of convective showers, cloud cover, or sea-breeze effects suppressing the maximum at the airport site. The settlement source is London City Airport Station on Wunderground, so the key dependency is the station-specific peak rather than a broader London average, which can matter if central London runs hotter or cooler than the airport.[Market description] If forecast models edge the day warmer, the YES side can re-rate quickly; if rain and cloud persist, the 0% implied probability may still look generous for NO but leaves little room for a surprise.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to Who Will Win, which mirrors the Polymarket order book directly.

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. 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 Who Will Win trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.