Highest temperature in London on August 3?

Platform comparison

Market context

London’s temperature on 3 August will be judged by the highest reading at London City Airport, with settlement tied to the Wunderground daily history page rather than a citywide average. That makes the contract sensitive to a single afternoon spike, and it can only resolve once the following day’s first datapoint is published, so late revisions still matter within the window.

The current 0% crowd price on the highest-temperature contract is not consistent with the published trading view on similar markets, where the Polymarket event is already leaning towards a peak around 30–31°C, with a forecast from the Met Office cited there at 31–32°C under sunny conditions. Recent UK heat has also been material: Sky News reported 26.6°C at Kew Gardens as London’s hottest day of 2026 so far, while BBC coverage said the south-east was under a red heat warning and that England could still see peaks in the low-to-mid 30s Celsius. That history matters because London summer maxima often cluster around the high 20s or low 30s, but a specific airport station can run a degree or two either side of the wider city reading.

For traders, the key catalyst is the live weather evolution rather than any on-chain mechanism, since the contract ultimately pays out in USDC once the oracle-style resolution source is finalised. The practical watch-items are the Met Office short-range forecast, any heat-health updates, and whether the morning cloud cover or sea-breeze suppresses the afternoon top end; if those hold, the distribution shifts materially away from the lower brackets. Because this is a crypto market, nearby BTC and ETH volatility may affect secondary liquidity and spread behaviour, but the underlying driver remains the London forecast and the exact station print.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reads Highest temperature in London on August 3? on-chain. Polymarket's quote comes directly from the Polygon order book — the only comparable venue with on-chain settlement. Kalshi (USD, off-chain), Betfair (GBP/EUR, off-chain) and Manifold (play-money) are listed alongside for venue context. Every CTA routes to BTC Prediction, which mirrors the Polymarket order book directly.

Resolution & payout

Settlement is on-chain via UMA Optimistic Oracle. A proposer posts the outcome with a bond, a two-hour dispute window opens, then the smart contract lifts winning conditional tokens to 1 USDC and sends payments to holders' wallets automatically. No withdrawal fees beyond Polygon gas.

Off-chain venues (Kalshi, Betfair, Smarkets) settle in local fiat through bank-side clearing — faster than SWIFT, slower than on-chain. Manifold pays no real cash.

FAQ

What are crypto prediction markets?

Crypto prediction markets are on-chain smart contracts where you buy YES or NO shares on a future crypto event (e.g. "BTC above $100k by year-end"). The market price between 0¢ and 100¢ is the implied probability.

What does a transaction cost on Polygon?

Polygon gas is typically under $0.01 per transaction. A full trade cycle (Approve + Order + Fill) totals around $0.03 — compared to $5-50 on Ethereum mainnet.

How does UMA secure the resolution?

The UMA Optimistic Oracle uses a bond system: a proposer posts a bond, a two-hour challenge window opens. On dispute the losing side forfeits the bond — financial incentive for honest resolution.

How volatile are crypto prediction markets?

Crypto markets react to spot prices — a 5% BTC move typically shifts a "BTC above X by date" market 10-20%. Polymarket crypto market liquidity is usually six-figure USD, sufficient for active trading.

Are crypto prediction markets taxable in the US?

In the US, prediction market gains are typically treated as ordinary income or short-term capital gains depending on holding period. Consult a tax professional for your specific situation — we cannot provide tax advice.