Highest temperature in London on August 7?

Platform comparison

Market context

London’s highest temperature on 7 August will be set by the warmest reading in Weather Underground’s **Daily Observations** for London City Airport, so the practical task is to track the intraday maximum rather than the summary high/low line. In programme terms, that means polling the station feed, watching for late updates, and mapping the observed Celsius value into the market’s outcome bands before the settlement window closes at 12:00 UTC.

The current 0% YES price sits well below the sort of late-summer London outcomes implied by recent forecasts. AccuWeather shows London around **25°C** for 7 August, while coverage from the time of the event says London was expected to reach about **26°C** with sunny intervals, which would place the outcome in the mid-range brackets rather than the hottest bins. More broadly, the Met Office has said summer 2026 temperatures have been running above average, but not at record levels so far, which supports modelling this as a moderate-heat case rather than an extreme spike.

For a power-user, the main catalysts are the day-of forecast revisions, any cloud or shower timing, and whether Heathrow or nearby London stations show a warmer air mass than expected as the afternoon develops. Conditional orders tend to matter here because the distribution can shift quickly if the forecast nudges from 25–26°C towards 27°C or higher, while a cooler marine flow pushes the highest reading back into lower buckets. The key dependency is simple: if the airport station never prints a reading above the forecast band, the market will settle on the lower temperature range even if other parts of London feel hotter.

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.

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.

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.