French authorities launch probe into weather bet manipulation
French officials have started an investigation after a bettor won $34,000 on a weather wager, amid suspicions that the temperature sensor at Paris’ Charles de Gaulle Airport was intentionally meddled with. Since early April, the airport has recorded abrupt evening temperature spikes that coincided with high-stakes bets placed on Polymarket, one of the world’s largest prediction platforms.
Ruben Hallali, CEO of climate risk firm Sereno, said his system flagged the anomalies in two incidents. The first, on 6 April, temperatures jumped from 18°C to 21°C before easing back. Nine days later, readings surged from 16°C to 22°C in just 30 minutes, then fell again to 16°C. Both peaks set the daily maximum temperature, the key metric for weather bets, fuelling suspicions of manipulation.
Formal complaints and investigation
According to Météo-France, it filed a complaint with the Air Transport Gendarmerie Brigade and the Bobigny Public Prosecutor’s Office, raising concerns about possible tampering with automated data systems.
Authorities are now investigating whether the anomalies were engineered to sway prediction market outcomes. Reports suggest wagers totalling $1.4 million were placed on Polymarket during the suspicious days. Moreover, speculation has swirled online with some outlets suggesting a hairdryer may have been used to heat the sensor, though no evidence has confirmed this.
Airport weather sensors are particularly vulnerable. Once they are exposed to the elements, they are reliant on single-source data and directly feed into both aviation safety systems and prediction markets. Investigators suspect simple tools, such as portable heaters, could distort readings, underscoring systemic risks in meteorology and decentralised finance.
Météo-France acknowledged these irregularities, stating: “In view of physical findings on one of our instruments and the analysis of sensor data, Météo-France was indeed led to file a complaint for alteration of the operation of an automated data processing system with the Air Transport Gendarmerie Brigade of Roissy.”
Market fragility and wider risks
The latest case reveals the fragility of prediction markets that rely solely on a single data source. While the manipulation may have been brief, this can easily destroy trust and discourage participation. Additionally, analysts warn that weather-linked contracts often hedge energy and agricultural bets. In other words, when they distort readings, they could cascade across broader markets.
Wisconsin DOJ is suing Kalshi, Robinhood, Coinbase, Polymarket, https://t.co/KZ3LXzxwIl, and their affiliates, to halt their alleged facilitation of illegal sports betting, a form of unlawful commercial gambling, in Wisconsin. pic.twitter.com/Jf8PMecXRq
— Attorney General Josh Kaul (@WisDOJ) April 24, 2026
Regulatory backlash
Scrutiny is growing towards Polymarket and similar platforms after this incident. For instance, European regulators have already ordered several operators to halt trading, citing legal and consumer protection concerns.
In the United States, the Wisconsin Department of Justice recently filed lawsuits against prediction markets, including Kalshi, Robinhood, Coinbase, Polymarket, and Crypto.com, seeking to block them from offering sports-related contracts.
The controversy adds to a string of scandals. A U.S. Army soldier, Gannon Ken Van Dyke, was charged over alleged Polymarket trades linked to classified information. Earlier this month, Polymarket faced criticism for allowing bets on the fate of U.S. pilots shot down in Iran. In January, the platform drew suspicion of insider trading after wagers tied to U.S. military action in Venezuela.
Additionally, these platforms continue to create a divide. For one, the U.S. Commodity Futures Trading Commission (CFTC) continues to assert federal authority, while most of Europe classifies them as gambling under the EU’s MiCA framework. This split is fuelling lawsuits, bans, and compliance battles worldwide.
Stay in the loop and join the biggest iGaming Community in the world with SiGMA’s Top 10 news countdown. Subscribe HERE for weekly updates from the world’s iGaming authority and exclusive subscriber-only offers.
