Highest temperature in London on July 31?

Platform comparison

Market context

Polymarket is currently pricing this London temperature contract at **0% YES**, which means the market is treating a qualifying high reading at London City Airport Station on 31 July as effectively off the table. Because settlement is based on the highest temperature recorded at London City Airport Station on the day, the relevant trade is not about London in general but about one specific observing site, one calendar day, and the final Wunderground daily maximum in Celsius. On Polymarket, that view is expressed via USDC positions on Polygon and settled through conditional tokens, so the last published temperature bucket at the reference station is what ultimately matters.

For context, London has seen extreme July heat before, but the recent upper bound for the capital is far above what most summer days deliver. The Met Office lists Heathrow at 37.8°C on 31 July 2020 among the UK’s highest July readings, and notes London entries in the mid-to-high 30s on other exceptional summer days.[1][2] London’s climate, however, is usually much cooler than those spikes, and even during warmer spells the city often sits in the high 20s or low 30s rather than the upper 30s.[14][16] That gap helps explain why a 0% reading can persist if the market believes the day has already failed to produce a plausible late-afternoon surge.

The main catalysts are the intraday forecast track, the timing of the day’s peak, and whether any late convective or advective heat develops before the Wunderground daily summary closes. Forecast reporting ahead of the event pointed to London reaching around 31-32°C with hotter pockets elsewhere in the region, while broader UK updates described a continuing heatwave and renewed 30°C-plus conditions in southern England.[11][16] For traders, the practical watchpoints are the afternoon high, any sharp cloud or shower development, and the final Wunderground entry for London City Airport Station once the day’s maximum is locked in.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to PolyGram, which mirrors the Polymarket order book directly.

Resolution & payout

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

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 PolyGram. 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'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.