Highest temperature in London on July 31?

Platform comparison

Market context

Polymarket prices this contract at **0% YES** today, which is consistent with a market that has already passed its settlement window and is effectively waiting for the Wunderground reading to finalise on London City Airport’s history page. On-chain, traders would have entered or exited via **USDC** on **Polygon**, with the position represented by **conditional tokens** that pay out according to the published maximum temperature band once the market resolves.

For context, London’s late-July heat profile is volatile rather than extreme by default: Met Office data show Heathrow reached **37.8°C** on 31 July 2020, while London’s July record high is higher still at **37.5°C** in the long-run climate tables for the city itself, and the UK’s all-time record stands at **40.3°C** from Coningsby in 2022.[3][17][18] That means a market tied to a single airport station can settle very differently from broader “London” headlines, especially if cloud cover, sea breezes or an earlier afternoon peak cap the reading before the day’s later warmth arrives.[3][8]

A trader watching the close should focus on the final Wunderground post for **London City Airport (EGLC)**, because the market rules say only the finalised daily maximum counts and later revisions are ignored.[8] The practical catalysts are the day’s hourly progression, any late convective showers, and whether the airport’s official maximum lands in the same range as nearby central London stations; in hot spells, Heathrow and Kew have historically printed several degrees apart even on the same date.[3][16]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track 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

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 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 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.