Highest temperature in London on July 31?

Platform comparison

Market context

The event here is the highest temperature recorded at London City Airport on 31 July 2026, with the market paying out according to the Celsius band that contains that day’s peak reading. In plain terms, a **YES** share on one band means the final reported maximum falls inside that band; a **NO** share means it does not. Because the settlement source is Wunderground’s daily history page for London City Airport, the key detail is the station’s final maximum for the full day, not an early afternoon reading or a city-wide average.

A 0% implied probability for **YES** on any one band is only meaningful if the market is already close to fully concentrated in another outcome, because London can and does deliver a wide spread of summer maxima. London’s recent extremes show the ceiling can be very high: Heathrow reached **37.8°C** on 31 July 2020, while the London record was **40.2°C** at Heathrow and St James’s Park during the July 2022 heatwave.[2][13] By contrast, more typical July readings are much lower, and even within hot spells small changes in cloud, wind, and sea-breeze influence can shift the final airport maximum by several degrees.

For traders, the main catalysts are the day’s weather forecast updates, any heat warning from the Met Office, and the timing of the airport station’s final reported observation. Recent UK coverage has already shown another hot spell pushing temperatures above **30°C** in parts of southern England, with London repeatedly among the warmer areas.[16] For a newcomer, the practical point is that prediction-market prices move on how likely each final temperature band looks after fresh forecast runs, but resolution waits for the official daily high at the specified station, which can settle only once the day’s data are complete.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on July 31? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

Resolution & payout

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

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 Prediction Market UK. 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.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Prediction Market UK trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.