France's national weather service, Météo France, has filed a criminal complaint with the gendarmerie at Roissy airport, alleging that an individual used a hairdryer or similar heating device to manipulate a temperature sensor at Paris Charles de Gaulle (CDG) Airport. The manipulation allegedly enabled the perpetrator to earn approximately $34,000 on the decentralized prediction market Polymarket.
Two Temperature Spikes Trigger Investigation
According to reports from Le Monde and BFMTV, two suspicious temperature anomalies occurred at the CDG weather station. On April 6 at around 6:30 PM local time, the sensor recorded a sudden increase of about 4°C within 12 minutes, briefly reaching 22.5°C before returning to normal. A second incident took place on April 15 at approximately 9:30 PM, when the reading jumped to 22°C under calm, cloudy skies and then dropped rapidly. Neighboring stations recorded no such changes, and wind direction nor relative humidity shifted during either event.
Meteorologist Points to Physical Interference
Paul Marquis, a meteorologist and founder of E-Meteo Service, told Le Figaro that a natural explanation is highly unlikely. “There was no change in wind direction or relative humidity, and no other station recorded anything. Physical interference with a heating device placed near the sensor probe is the most logical explanation,” Marquis said. The CDG station sits near the airport perimeter, accessible from a public roadside area, making it vulnerable to tampering.
Direct Link to Polymarket Payouts
Polymarket uses data from that specific station for its “Paris Daily High Temperature” prediction markets. On April 6, low-odds bets on Paris reaching 21°C paid out roughly $14,000 to one or more accounts created just days earlier. On April 15, a similar wager on 22°C yielded about $20,000, bringing the total illicit gains to $34,000. Polymarket users flagged the activity in real time, with comments suggesting manipulation and insider knowledge.
Platform Switched Data Source, Investigation Ongoing
Around April 19, Polymarket changed the official data source for its Paris temperature markets from CDG to the sensor at Paris–Le Bourget Airport, effectively removing the compromised station from its settlement process. Météo France confirmed the criminal complaint but declined further comment. No arrests have been made, and no suspects have been publicly identified. The case has drawn attention in French weather forums like Infoclimat.fr and spread rapidly on X, prompting coverage by major outlets including Le Monde, Le Figaro, and BFMTV. The incident highlights a fundamental vulnerability in prediction markets that rely on a single physical sensor: when one data point controls financial outcomes, it becomes a target. Investigations remain active.