Highest temperature in London on July 31?

Platform comparison

Market context

London’s maximum at City Airport on 31 July is the key settlement input, and the market is effectively pricing the afternoon peak rather than the morning or early-evening reading. The crowd-implied 0% for YES looks extreme against the historical range, because London can and does get into the mid-to-high 30s Celsius in late July: Heathrow reached 37.8°C on 31 July 2020, while the all-time England record of 40.3°C was set in July 2022.[3][10][17]

That said, the distribution matters more than the headline extremes. London’s July daily highs usually sit in the low-to-mid 20s Celsius, and even warmer spells often top out around the high 20s or low 30s unless a broader heatwave develops.[8][18] By comparison, a 0% yes price would imply traders see the contract’s target range as essentially unreachable; if sportsbook-style weather pricing is reflecting similar assumptions, it is likely anchored to a more ordinary London July rather than a heatwave scenario. The historical analogue to watch is 2020: London’s hottest reading came from Heathrow, not the city centre, showing how the exact station and microclimate can shape the final number.[3][5]

For traders, the main catalysts are the late-morning and early-afternoon temperature ramps, cloud cover, wind direction, and whether the south-east stays under any continental heat plume. Forecasts have recently shown London capable of pushing into the low 30s in heatwave conditions, with one current report discussing 32°C in London and 31–32°C across nearby southern cities under hot July weather.[12][18] Because the market resolves on the highest reading for the day, a brief spike around midday to mid-afternoon matters more than the headline daily average, and the gap between London City Airport and other London stations can be decisive.[2][3]

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

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

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 Best Prediction Markets. 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 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 Best Prediction Markets 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.