Highest temperature in London on August 3?

Platform comparison

Market context

London has started the day with a forecast pointing to a warm, dry spell, with daytime highs around the low 30s Celsius in several current outlooks and little sign of meaningful rain early on.[2][3][5] That matters for this market because the settlement is based on the *highest* temperature recorded at London City Airport rather than an average, so a single strong afternoon peak is enough to drive the result.[2]

The crowd’s 0% YES looks easy to understand only if it is being read against London’s usual August climate, where long-run expectations are much cooler, typically around 21-22°C for daytime highs, with some sources citing monthly averages closer to 22°C and others showing a broader forecast range that tops out in the high 20s to upper 30s Fahrenheit-equivalent.[1][6][7][16] Even so, comparable summer setups in the city can produce brief spikes well above the monthly norm, especially when skies stay mostly clear and wind is light; the current forecast shows exactly that sort of pattern, with sunshine, low precipitation odds and modest wind through the daytime hours.[2][3][5]

For traders, the key catalysts are the midday heating trend, any late-morning cloud build, and whether Heathrow- or central-London-style forecasts prove too cool or too warm relative to the airport reading used for settlement.[2][3][17] Any sudden shift in shower cover, sea-breeze influence or wind direction could cap the maximum, while the market will only care about the single highest hourly or observed reading posted for London City Airport on the day.[2][3][13]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on August 3? 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 Prediction Today. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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 Prediction Today 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.