Météo France, the French national meteorological service, has filed a criminal complaint with the gendarmerie of the Roissy airport transport brigade for “alteration of the functioning of an automated data processing system.” The complaint follows two temperature anomalies recorded at the automated weather station at Paris Charles de Gaulle Airport (CDG), which apparently coincided with winning bets totaling approximately $34,000 on the crypto-based prediction platform Polymarket.
Suspicious Temperature Spikes
According to Météo France, the first anomaly occurred on April 6 at around 6:30 PM local time. The sensor recorded a rise of about 4 degrees Celsius within 12 minutes, briefly reaching 22.5°C before returning to normal. The second event took place on April 15 at approximately 9:30 PM, when the temperature climbed to 22°C under partly cloudy skies, then dropped again within minutes. Notably, no neighboring weather stations recorded similar fluctuations during either period, and wind direction and relative humidity showed no corresponding changes.
Paul Marquis, a meteorologist and founder of E-Meteo Service, told Le Figaro that the pattern is difficult to explain by natural causes. “There was no change in wind direction or relative humidity, and other stations recorded nothing,” he said. “The most plausible hypothesis is physical intervention with a heating device placed near the sensor probe.” The CDG station is located near a runway perimeter and accessible from a public road, making it feasible to approach the sensor without authorization.
Polymarket Bets & Data Source Change
Polymarket used data from that specific CDG station to settle markets for Paris daily high temperatures. Reports indicate that on April 6, a bet placed on Paris reaching 21°C paid out approximately $14,000 to a user whose account had been created just days earlier. On April 15, a similar bet on 22°C yielded another $20,000 for a different user. The combined winnings reached roughly $34,000. Polymarket users flagged the activity in real time, with comments alleging manipulation and insider trading. The platform is banned in France but remains accessible to some users inside the country.
Following widespread media coverage, Polymarket switched its Paris temperature resolution source from CDG to the sensor at Paris-Le Bourget airport around April 19, eliminating further dependence on the compromised location.
Investigation & Implications
The incident first gained attention on French weather forum Infoclimat.fr, where users flagged the April 6 data as suspicious within hours. Discussions then spread to X (formerly Twitter), with posts referencing a “hair dryer at a Paris airport” going viral and being picked up by major outlets including Le Monde, Le Figaro, and BFMTV. Météo France declined further public comment beyond confirming the complaint. No arrests or suspect identifications have been announced as of writing. The case highlights a practical vulnerability in prediction markets that rely on a single physical sensor: when one data point controls the outcome of a financial market, it becomes a target. The investigation remains open.