Highest temperature in London on July 7?

Platform comparison

Market context

On Monday, London City Airport recorded a peak of 34°C as a major heatwave gripped southern England, with the Met Office confirming temperatures will remain above 32°C through the middle of the week. This current intensity frames the 0% implied probability on the 31°C market as a clear mispricing; historical data shows July is the capital’s warmest month, and recent extremes like the 40.2°C record at Heathrow in 2022 prove that hitting 31°C is routine during such surges, not an anomaly.

Traders must watch the escalating risk of thunderstorms forecast for the evening of 7 July, which could disrupt the day’s maximum if heavy downpours arrive before the peak heat, though the Met Office currently predicts the heatwave will persist until at least Sunday. The UK Health Security Agency has issued yellow heat alerts covering London from 4 July to 11 July, underscoring the severity of the conditions. When comparing platforms, Polymarket’s decimal odds format may obscure the stark divergence from Kalshi’s implied probability model here, while Betfair’s fee structure and Smarkets’ lower charges could alter the final settlement value compared to platforms with stricter KYC requirements that limit liquidity on such weather-specific events.

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Methodology

This page compares Highest temperature in London on July 7? 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 Robinhood Prediction Markets, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Settlement is the biggest difference between the four platforms: Polymarket on-chain in USDC (instant), Kalshi USD via CFTC (T+1), Betfair and Smarkets in local currency via bank withdrawal (T+1 to T+3). On-chain settlement clears in minutes — the fastest payout path of the four.

FAQ

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.

Is Betfair a Polymarket alternative?

Only partially. Betfair Exchange is UK-focused with a sports-betting emphasis; they have politics markets but with thinner liquidity than Polymarket. Settlement in GBP/EUR, 2-5% commission on winnings.

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.

Are all these platforms regulated?

No. Kalshi is CFTC-regulated (US). Betfair and Smarkets are UK Gambling Commission licensed. Polymarket operates without explicit regulation — a different risk profile than a regulated sportsbook.

Which platform supports Klarna/SOFORT?

Directly: none. Polymarket accepts only USDC on Polygon. Robinhood Prediction Markets offers a fiat on-ramp via Klarna or SOFORT (DE/AT/CH) and converts internally to USDC for the Polymarket order book. T+1 processing.