Highest temperature in London on July 13?

Platform comparison

Market context

London City Airport is forecast to reach a high of 27°C today, yet the prediction market betting on a temperature exceeding this threshold carries only a 7% implied probability. This low figure reflects the station’s typical July average high of 22°C, though record-breaking heatwaves have previously pushed London temperatures well above 35°C, with the all-time city record of 40.2°C set at Heathrow in July 2022[5]. Historical data shows that while extreme heat is rare at EGLC compared to inland sites, the Met Office has recorded 35°C or higher in May, June, and July for the first time in UK history, suggesting the 7% probability may understate the risk of a sudden spike[3].

Traders monitoring this market should watch real-time updates from the Met Office and Wunderground, the official resolution source, as southerly winds and falling pressure currently indicate potential for rising temperatures[6]. The settlement window closes at 12:00 UTC on 13 July 2026, meaning any late-morning heat surge could alter the outcome before resolution. Platform comparisons reveal key divergences: Polymarket displays outcomes as implied probabilities (here, 7% YES), whereas Kalshi and Betfair use decimal odds, and Smarkets focuses on spread betting with lower fees but stricter KYC requirements. These structural differences affect how traders interpret the 7% figure, with some books offering more liquidity on temperature ranges while others prioritise fee efficiency over speed.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares Highest temperature in London on July 13? 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.

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.