Highest temperature in Paris on August 11?

Platform comparison

Market context

Paris’s highest temperature on 11 August will be set by the reading at Paris-Le Bourget Airport, and the market resolves off Weather Underground’s **Daily Observations** table rather than the summary high. That detail matters because the current crowd price of 0% YES on Polymarket is a statement about the exact Celsius band at that station, not about a generic citywide “hot day”; on prediction venues such as Betfair, Smarkets and Kalshi, the same event can look different once you factor in decimal odds, platform fees and whether your account is even KYC-cleared for the market.

For context, early-August Paris usually sits in the mid-20s Celsius for daytime highs, but the city can move sharply higher during warm spells. AccuWeather’s forecast for 11 August points to 91°F, or about 33°C, while other forecasts cluster around 32°C, which sits above the long-run August average but well below the city’s extreme records near 40°C.[2][6][18] That makes the current 0% YES reading notable: on a venue like Polymarket, the market is effectively treating the relevant temperature band as extremely unlikely, while on an exchange-style book the same view would typically be expressed through back/lay pricing rather than a simple implied-probability display.

The main catalysts are the day’s actual station observations and any late forecast revisions from the weather services traders use to anchor expectations. AccuWeather currently has a Yellow Warning for Extreme High Temperature in Paris for 11 August, which signals heat risk but does not guarantee a particular final reading.[12] Because the contract resolves from the first published following-day datapoint after the observation window closes, traders will be watching whether the Le Bourget hourly sequence peaks before midday UTC and whether later corrections alter the record; that timing is especially important on platforms with different cut-offs, liquidity and fee treatment, since a narrow temperature band can trade very differently across Polymarket, Kalshi, Betfair and Smarkets.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares Highest temperature in Paris on August 11? 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, 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 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.