Highest temperature in London on July 19?

Platform comparison

Market context

London City Airport recorded a cool 15°C high on 19 July 2026, confirming the market’s 0% YES probability for any extreme heat outcome. The day remained cloud-free with a gentle northern breeze, aligning closely with the 0% crowd-implied chance that temperatures exceeded typical summer ranges. This actual reading sits well below the long-term July average high of 23.9°C for the station, reinforcing the market’s certainty that no record-breaking heat occurred.

Historically, July highs at EGLC rarely breach 26°C, with only isolated heatwaves in 2018 and 2022 pushing past 30°C. The 15°C reading on 19 July falls into the lower quartile of recent July days, matching patterns seen during cooler, maritime-influenced weeks. Traders should note that the 21°C frontrunner on Polymarket now reflects a resolved outcome, as the actual temperature was 4°C below that threshold, validating the initial 0% pricing.

No further catalysts remain for this settled market, but traders monitoring similar weather events should watch the Met Office’s weekly climate summaries for early signs of upcoming heatwaves. Recent forecasts for late July suggest a potential shift toward warmer conditions, with maximums projected near 26°C by 25 July [4]. For now, the focus shifts to new weather markets where volatility remains active.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on July 19? 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

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.

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.