Highest temperature in London on July 23?

Platform comparison

Market context

Polymarket has this contract **broadly around 26°C**, with the live market showing 26°C as the frontrunner and 27°C close behind, while the 0% YES price suggests the crowd is currently assigning almost no value to the event landing in the YES range as defined by the market structure.[2] Because settlement is tied to the **highest temperature at London City Airport Station** on 23 July, the key question is not London’s citywide average, but the single daily maximum recorded on Wunderground for EGLC, which can differ from broader city forecasts.[1]

That framing matters because July in London usually sits in the low-to-mid 20s Celsius, but hotter spells can lift daily highs into the upper 20s or above 30°C.[1][5] Recent London coverage also pointed to model runs keeping temperatures in the late 20s and early 30s during mid-July, with peak values around 27°C before cooler conditions returned, which is the kind of pattern traders use to gauge whether a market like this should cluster around the mid-20s or break higher.[3] For a Polymarket user, the trade is ultimately a USDC position on Polygon via conditional tokens, so the practical issue is whether the station’s observed maximum prints inside the range you expect, not whether the broader public forecast feels warm.

The main catalysts are the day-of weather cycle, any late model shifts, and whether cloud cover, sea breeze, or scattered showers suppress the airport reading versus central London.[1][3] Traders should watch the morning forecast updates closest to the settlement window, because the contract resolves on the day’s recorded high rather than a forecast at noon, and the outcome can move materially if a warm airmass arrives or breaks down earlier than expected.[1]

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

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 Kalshi UK. 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.

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.