Highest temperature in Paris on August 4?

Platform comparison

Market context

Paris’s hottest reading on 4 August will be set by the maximum observed at Paris-Le Bourget Airport, not by a city-wide average, so the key question is whether the day peaks in the low 30s or pushes into a hotter tail. The market is currently priced at 0% YES, which is far below the summer climatology for Paris: August highs are typically in the mid-20s °C, although the city has already been through an exceptional 2026 heatwave, with Paris reaching 40.9°C in June and France recording its hottest-ever day in late June.[2][8][11][13]

For comparable reading, the platform angle matters. On Polymarket, the contract is shown in implied probability terms, so a 35% price on 31°C means the crowd is assigning that outcome roughly a one-in-three chance; Kalshi and Betfair-style books are usually easier to read as direct prices or decimal odds, while Smarkets often presents percentages/odds with exchange-style fees rather than a bookmaker margin. In weather markets, that distinction matters because a thin band of outcomes can move quickly when the forecast shifts by even 1-2°C, and the current 0% yes implies the market sees the named threshold or outcome bucket as effectively shut off.[3]

The main catalysts are the same ones that move all short-dated weather books: the latest Paris forecast, any overnight model updates, and whether clouds or a weak disturbance cap the daytime maximum at the airport station. August in Paris can still be warm and changeable, with forecast sources showing highs around the mid-20s to low-30s and some chance of rain, so the final print depends on the exact timing of heating and any convective showers rather than the monthly average alone.[4][12] Since the market resolves from Wunderground’s Paris-Le Bourget Airport history page at 12:00 UTC, traders on platforms with different settlement mechanics should also watch timestamp cut-offs closely; on exchange-style venues, fees and KYC access vary, so the same weather view may trade at different effective costs even when the directional read is identical.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares Highest temperature in Paris on August 4? 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

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.

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.

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.