Highest temperature in Paris on July 9?

Platform comparison

Market context

The real-world event is the peak of a third heatwave currently sweeping Île-de-France, with temperatures in Paris expected to reach up to 38°C on 9 July 2026[1]. This market resolves to the highest temperature recorded at Paris-Le Bourget Airport, sourced from Wunderground, and the current crowd-implied probability of 0% for a specific outcome suggests traders are betting against a narrow range rather than the heat itself.

Historical context frames this probability through the 2026 European heatwaves, where 35.1°C was recorded in nearby Surrey on 9 July, and France has already seen peaks of 40°C in June[3][5]. Comparable cases from May 2026 show Paris hitting 37.8°C, indicating that temperatures in the 32–36°C range are highly probable, making the 0% implied probability for a single specific range a reflection of market dispersion rather than a lack of heat[9].

A power-user approaching this programmatically should monitor Meteo France’s orange alert updates and the daily Wunderground feed for the Paris-Le Bourget station, as the settlement window closes at 12:00 UTC on 9 July[1]. The primary catalyst is the continuation of the heat dome, with no scheduled weather breaks expected before the settlement date, meaning the highest temperature will likely be determined by the afternoon peak rather than any sudden cooling event[5]. Traders should watch for real-time temperature spikes above 35°C, as these would invalidate any narrow-range bets and confirm the market’s dispersion.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

FAQ

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.