Highest temperature in London on August 3?

Platform comparison

Market context

London City Airport’s maximum temperature on 3 August is a straightforward weather print, but the market only settles on the *highest* reading recorded during the day at the station, not a citywide average. For a programme or bot, the useful approach is to model the event as a single daily max query against the Wunderground history page once the day is complete, then map the result into the market’s temperature band; before settlement, intraday swings matter more than the morning forecast. Current crowd pricing at 0% YES implies the market is either unavailable, mispriced, or still not being parsed correctly by participants, because the described resolution source is a standard daily maximum series rather than an exotic endpoint.[4][16]

Recent forecast pages point to a warm, summer-type setup for London in early August, with highs variously shown around the low-to-mid 20s Celsius and some sources pushing towards the high 20s or low 30s Celsius for the city.[1][2][3][4][6][14][17] That range matters because a maximum near 24–26C would sit close to long-run August norms, while a hotter afternoon would quickly push the print into a higher bracket; for automated trading, the key dependency is whether later forecast updates shift the expected peak temperature, since even a one-day change in cloud cover, wind, or rain probability can move the final band more than the overnight low can.[1][4][6][14]

For a power-user workflow, the main watchpoints are the final forecast refreshes, any late-breaking weather warning from UK forecasters, and the actual observed max at London City Airport as it appears through the day. Hourly forecast output already shows a warm and bright scenario for 3 August, with a daytime high around 83F and east winds, so a script that polls the forecast and then the Wunderground history endpoint near and after the settlement cut-off would capture the most relevant information chain.[4] If the afternoon remains sunny and dry, the market should be read as a temperature-band event rather than a rain-risk trade; if cloud or showers build in, the peak can undershoot the more aggressive forecast outputs.[2][4][5]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

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

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

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.