Highest temperature in Paris on July 17?

Platform comparison

Market context

Paris-Le Bourget Airport will record its peak temperature for 17 July 2026, with the market currently pricing a 28°C outcome at 34% and 27°C at 26%, while the specific “YES” contract for an unlisted threshold sits at 0% implied probability [1]. This divergence highlights how Polymarket’s multi-outcome format captures granular heat expectations that single-binary books on Kalshi or Betfair often obscure, forcing traders to compare decimal odds against implied probabilities across platforms.

Historical July highs at Paris-Le Bourget frequently exceed 25°C, with recent summers showing peaks near 28–30°C during heatwaves, making the 0% crowd-implied probability for the current binary contract appear misaligned with seasonal norms unless the threshold is set implausibly high. Kalshi’s weather contracts, which use decimal odds and require KYC, may offer tighter spreads on similar temperature ranges, whereas Polymarket’s permissionless access and lower fee structure attract volume on niche events like this, creating liquidity gaps between books.

Traders should monitor the Meteo-France heatwave bulletin and any European Environment Agency alerts issued before 12:00 UTC on 17 July, as these dictate official temperature thresholds and settlement triggers. A recent Meteo-France update noted elevated risk for mid-July heat in northern France, suggesting the 0% probability may reflect a threshold mismatch rather than genuine cold expectations [1]. Smarkets’ bet-backing model could reveal arbitrage if Kalshi’s odds on 28°C diverge significantly from Polymarket’s 34% share.

Sources: 1

Methodology

This page compares Highest temperature in Paris on July 17? 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

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

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.

Which platform is accessible globally?

Polymarket is geo-blocked in the US/UK/EU. Kalshi is US-only. Betfair and Smarkets are UK-restricted. Robinhood Prediction Markets 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.