A Hair Dryer May Have Gamed a Paris Weather Sensor for $34,000 on Polymarket

Someone may have used a hair dryer near a Paris airport weather sensor to win $34,000 on the prediction market platform Polymarket, prompting France’s national meteorological service to file a criminal complaint.

Key Takeaways:

• Météo France filed a complaint with Roissy airport gendarmerie after two CDG sensor anomalies on April 6 and April 15 aligned with Polymarket payouts totaling roughly $34,000.
• Meteorologist Paul Marquis of E-Meteo Service ruled out natural causes, concluding physical intervention with a heat device was the most probable explanation.
• Polymarket switched its Paris temperature resolution source to Le Bourget Airport on April 19, though no arrests have been made at the time of publication.

French Meteorological Service Files Complaint After Paris Airport Sensor Data Aligns With Polymarket Payouts

According to several reports, Météo France confirmed it filed a complaint with the Roissy air transport gendarmerie brigade for “alteration of the operation of an automated data processing system” after reviewing physical observations and sensor data from its automated station at Paris Charles de Gaulle Airport.

The complaint follows two temperature anomalies at the CDG station. On April 6, the sensor recorded a jump of roughly 4 degrees Celsius within 12 minutes at approximately 6:30 p.m., briefly reaching 22.5 degrees Celsius before returning to normal. On April 15 at approximately 9:30 p.m., the reading climbed to 22 degrees Celsius under calm, cloudy skies before dropping back within minutes.

No neighboring stations recorded similar changes during either event. Wind direction and relative humidity showed no corresponding shifts.

Paul Marquis, meteorologist and founder of E-Meteo Service, said the pattern is hard to explain naturally. “There was no change in wind direction or relative humidity, and the other stations recorded nothing,” Marquis told Le Figaro. He said a physical intervention with a heating device placed near the sensor probe was the most plausible explanation.

The CDG station sits near the runway perimeter and is accessible from a public roadside area. The Polymarket wagers use data from that station to resolve its Paris daily maximum temperature markets, making the sensor a direct input into financial outcomes.

On April 6, long-shot bets on Paris reaching 21 degrees Celsius paid out approximately $14,000 to at least one bettor whose account had been created days earlier, according to reporting by Le Monde and BFMTV. A similar wager on 22 degrees Celsius resolved in a bettor’s favor on April 15 for roughly $20,000.

The combined total from both events reached approximately $34,000. Polymarket users flagged the activity in real time, with comments citing manipulation and insider trading.

Polymarket is one of the largest crypto-based prediction markets in the world, allowing bets on weather, politics, sports, and other real-world events. The platform is banned in France but remains accessible to some users in the country.

Around April 19, the prediction market platform’s weather bets shifted the resolution source for Paris temperature markets from the CDG station to the sensor at Paris-Le Bourget Airport, cutting off further reliance on the compromised location.

Rule changes for Paris temperature market on Polymarket. The incident drew attention on French meteorology forums, including Infoclimat.fr, where users began flagging the April 6 data as suspicious within hours. Discussion spread to X, where posts referencing a “hair dryer at a Paris airport” went viral and helped push the story into mainstream French media outlets, including Le Monde, Le Figaro, and BFMTV.

Météo France declined further public comment beyond confirming the complaint. No arrests or suspect identifications had been announced at the time of writing. The case points to a practical vulnerability in prediction markets that settle against a single physical sensor. When one data point controls the outcome of a financial market, it becomes a target.

The investigation remains open.