Highest temperature in London on July 23?

Platform comparison

Market context

London is starting the day with warm, settled conditions rather than anything that would point to an exceptional spike later this morning. The latest crowd pricing still puts **0%** on the market’s top range, which is notable given that the implied frontrunner elsewhere in the book is only **26°C**, with **27°C** the next most likely outcome. That mix suggests traders are treating a mid-20s cap as the base case unless the forecast shifts sharply before the midday cut-off.[2][3]

For context, London’s July climate typically delivers highs around **23°C**, but heat can break higher on a handful of summer days, especially when a warm airmass lingers and cloud cover stays limited.[6] Recent weather commentary has also pointed to London’s July heat easing after the mid-month spike, with forecasts shifting back towards the high-20s rather than the low-30s.[4][9] The practical read-through is that a winning outcome usually needs a clean, sunny afternoon and no early shower activity to unlock the upper bands.

Traders should watch the short-range forecast cycle, especially cloud, wind and any thunder risk, because the settlement depends on the **highest** temperature reached at London City Airport before **12:00 UTC**. A morning upgrade in sunshine or a downgrade in convective cloud cover can move the day’s peak by a degree or two quickly, while any marine influence from the Thames estuary can limit the ceiling. If the current pattern holds, the market is still leaning towards a modest maximum rather than a breakout heat reading.[1][3]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on July 23? 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.

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.

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.

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 Today trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.