Highest temperature in Paris on July 23?

Platform comparison

Market context

Paris’s temperature on 23 July will be set by the day’s highest reading at Paris-Le Bourget Airport Station, and the current market is effectively pricing a **25°C** outcome as locked in with **100%** implied probability[1]. That makes the contract much more about whether the final official maximum lands in the 25°C band than about any broader debate on the day’s weather pattern[1].

Historically, Paris in July usually sits close to the mid-20s Celsius, with an average July high of about **26°C**, while typical daily highs across the month span roughly **20°C to 43°C**[2]. That context explains why the market looks tight around a single bucket rather than spread across several outcomes: a normal summer day in Paris often clusters near the same temperature range as the current frontrunner[2]. On Polymarket, this is shown as a direct implied-probability market; on Kalshi, a comparable contract would usually be read through price in cents and translated into an implied probability, while Betfair and Smarkets typically express the same view as decimal odds after exchange commission. For a trader comparing books, the practical difference is whether the edge sits in the quoted probability itself or in the all-in price after fees and access frictions.

The main catalysts are the afternoon heating profile, cloud cover, and any late-day convection or sea-breeze effects that can cap the maximum before the station’s daily high is finalised. For a same-day contract, the key dependency is not the evening temperature but whether the airport station records a peak above or below the 25°C band before settlement. Traders also need to account for venue rules: platform access, KYC availability, and whether fees are charged up front or netted from winnings can matter more than the headline price when the market is already effectively one-sided.

Sources: 1 · 2

Methodology

This page compares Highest temperature in Paris 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 Kalshi Alternative UK, 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.

Which platform is accessible globally?

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

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.