Highest temperature in London on August 5?

Platform comparison

Market context

London City Airport’s highest temperature on 5 August will be settled against the day’s observed maximum, so the market is really about whether the airport gets to the mid-20s rather than whether London broadly feels warm. Polymarket’s book is tightly packed around **25°C** and **26°C** at **36%** each, with **24°C** next at **21%**, which implies traders see a fairly narrow distribution and limited room for a surprise on either side.[1] That is more assertive than long-run August norms for London, which are materially cooler, but consistent with a short-range setup that has already turned warm in the capital.[9]

Comparable forecasts point to a modestly warm, not extreme, outcome. Recent coverage on 5 August called for sunny intervals and a high of **25°C**, while another forecast cluster showed most model outputs sitting between **24°C and 26°C**, with only small variation from cloud cover or a weak frontal passage.[3][5] The fact that the market’s leading outcomes are evenly split between 25°C and 26°C is in line with that model spread, while the **0% YES** crowd-implied price on the specific contract suggests little appetite for an outlier print relative to the forecast consensus.[1][5]

The main catalysts are late-morning and early-afternoon heating, cloud timing, and any drizzle or sea-breeze influence affecting London City Airport more than inner London. Polymarket’s own market notes say revisions to temperatures during the window can still count until the first datapoint for the following date is published, which means traders will watch the station feed and Wunderground updates closely right through the settlement cut-off.[1] Outside the market itself, the UK’s broader summer pattern has already featured heat episodes and warm southern conditions this season, but the immediate driver here is the local day-of forecast rather than any national heat headline.[10][11]

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 PolyGram, which mirrors the Polymarket order book directly.

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