Highest temperature in London on July 23?

Platform comparison

Market context

The relevant event is the maximum temperature recorded at London City Airport on 23 July 2026, with settlement tied to the daily high on Wunderground rather than to a broader London average. Early market pricing on Polymarket puts 26°C as the frontrunner at 48%, with 25°C next at 24%, which implies the crowd is leaning towards a warm but not extreme summer day. By contrast, other venues usually present the same weather range through different market mechanics: Polymarket shows direct implied probabilities, while Kalshi-style contracts are typically quoted in decimal-style prices and Betfair or Smarkets expose back/lay prices with exchange fees rather than a simple yes/no probability.

For context, London’s July climate normally centres on mid-20s highs, with average expectations around 23°C and precipitation that does not prevent warm afternoons, so a 25–26°C settlement is broadly in line with seasonal norms. July can still produce sharper spikes, however: recent reporting on London’s July heat spells showed temperatures reaching 35°C earlier in the month, underlining how quickly the distribution can shift when a warm airmass settles over the capital. That makes today’s 0% YES crowd reading look less like a forecast of cool weather than a reflection of how the market is defined against a specific temperature band and settlement source.

Traders should watch for the day’s high to be set by local cloud cover, wind direction and any short-lived showers over east London, because City Airport can differ from central London by a degree or more on marginal days. The key dependency is the official hourly progression on Wunderground for EGLC, not headlines about London generally. On Polymarket, the spread between 25°C and 26°C is the main signal; on exchanges such as Smarkets or Betfair, fees and liquidity can make that same two-degree decision look cheaper or more expensive than the headline probability suggests.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares Highest temperature in London on July 23? specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. The live probability is the Polymarket mid; the comparison columns summarise each venue's fee structure, KYC, settlement currency and payment rails. Every CTA routes to Polymarket Alternative, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Polymarket settles via UMA Optimistic Oracle on Polygon. A proposer posts the outcome with a bond, the two-hour window runs, then the smart contract pays USDC.

Kalshi settles USD through the CFTC-regulated clearinghouse — the cleanest variant, with heavier KYC. Betfair Exchange settles in account currency (GBP/EUR), net of 2-5% commission. Smarkets follows the same model as Betfair with a lower default 2% commission.

FAQ

Polymarket vs Kalshi — which is better?

Depends on your location. Kalshi is CFTC-regulated, US-only with full KYC. Polymarket is global, on-chain, no KYC up to $1,500. Polymarket has ~10x higher liquidity but higher regulatory risk.

What does Polymarket cost vs Kalshi?

Polymarket: 0% fees, only Polygon network costs (~$0.01/trade). Kalshi: up to 7% per trade plus spread. For high-frequency traders, Polymarket is dramatically cheaper.

Which platform has the deepest liquidity?

Polymarket — by a wide margin. Top markets reach $50-500M volume, Kalshi ~$200M cumulative, Betfair similar. Deeper liquidity means your trade moves the quote less.

What about Smarkets as an alternative?

Smarkets is a UK betting exchange with a lower default commission (2%) than Betfair. Liquidity on political markets is below Polymarket, comparable to Kalshi. Geo-blocked in many jurisdictions.

Which platform is accessible globally?

Polymarket is geo-blocked in the US/UK/EU. Kalshi is US-only. Betfair and Smarkets are UK-restricted. Polymarket Alternative has a different geo footprint and routes to Polymarket's order book at 0% fees.