Pronóstico: Highest temperature in London on July 31?

Platform comparison

Market context

Polymarket is pricing **0% YES** on a contract that settles to the highest temperature recorded at London City Airport on 31 July, paid out in USDC on Polygon through conditional tokens. For a user buying or selling here, the key point is that the market is not asking whether London gets “hot”, but which Wunderground temperature band the day’s peak lands in before the noon UTC settlement cut-off, with the final source being the station’s daily history page.

That 0% read sits against a London summer profile that can still produce sharp spikes, but the ceiling is usually well below Britain’s headline extremes. London’s city-centre and airport records show how quickly conditions can jump: Heathrow reached 37.8°C on 31 July 2020, while the UK’s all-time high of 40.3°C was set in Coningsby during the 2022 heatwave[1][2][8][10]. For context, London’s climate averages are far cooler than those peaks, so the market is mainly a bet on whether the day comes in at a very specific, elevated but not extraordinary band[11][14].

A trader watching this contract would focus on same-day forecast updates, airport observations, and whether a broader UK heat event is building over the southeast. Recent reporting from the BBC noted 2026 had already seen repeated 34°C-plus days and projected upper-20s to low-30s Celsius across England and Wales, with the southeast still capable of reaching 33–35°C in hot spells[16]. In practice, the settlement will hinge on the final reported high at London City Airport rather than regional averages, so late-afternoon temperature trends, sea-breeze effects, and any shift in the warmest hour matter more than the morning forecast.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Pronóstico: 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

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

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 Polymarket Qué Es. 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.

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.

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.