Apr 26, 2026
The odds of the temperature exceeding 22 degrees Celsius at Charles de Gaulle airport in Paris on April 6 were less than 1%, Polymarket said. It gave the same odds on April 15. But one individual seemingly found a way to rig the system and walked away $34,000 richer.
Law enforcement authorities in France are investigating if the weather monitoring device at the airport (the world's seventh busiest for international passengers (1) was tampered with after it recorded a very brief, dramatic spike of six degrees (2) in seconds on the days of the winning bets from an anonymous trader who went by the username "xX25Xx". The investigation is still ongoing, but the leading theories are that the culprit used either a battery-powered hair dryer or a lighter to briefly spike the temperatures.
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The user deleted his account after the second win, where they racked up $21,398 in profits on a $119 bet. There is no indication that Polymarket forced them to return their winnings (3).
The dangers of messing with weather equipment
While the online world is having a good laugh at someone creatively cheating on the wager, officials are taking the incident seriously.
Météo-France, the country's national meteorological service, filed the complaint with police. Air temperature is one of the pieces of data used to determine things like the proper takeoff distance for planes as well as their climb rate. Spikes can throw off those calculations, which can impact and potentially endanger planes and passengers.
Polymarket is still hosting meteorological bets for Paris, but the site no longer uses temperature readings at Charles de Gaulle as the authoritative number. Following Météo-France's complaint, the platform began using readings from Paris-Le Bourget, a smaller airport in the Paris region.
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A pattern of scandal
xX25Xx's big win was hardly the first by suspicious circumstances on a prediction market. On Thursday, the Justice Department announced (4) a U.S. soldier named Gannon Ken Van Dyke had been arrested and charged for placing bets on Polymarket using classified information he had access to regarding the capture of former Venezuelan president Nicolás Maduro.
"Prediction markets are not a haven for using misappropriated confidential or classified information for personal gain," said U.S. Attorney Jay Clayton (5).
Van Dyke allegedly bet just over $33,000 on the markets before the military action, winning nearly $410,000, officials say. He's charged with three counts of violating the Commodity Exchange Act, each of which carries a maximum sentence of 10 years in prison; one count of wire fraud, which carries a maximum sentence of 20 years in prison; and one count of an unlawful monetary transaction, which carries a maximum sentence of 10 years in prison.
Critics have long pointed to the potential for scandal on prediction markets like Polymarket and Kalshi, noting some participants use insider information when placing bets, the anonymity of accounts and a general lack of oversight.
The lack of enforcement over questionable trades, though, might be temporary, says King & Spalding. Should Democrats take the White House in 2028, that could mean trouble for people who have played fast and loose with the rules.
"Even if the Trump administration does not end up aggressively policing insider betting on prediction markets, the statutes of limitations for some [potentially illegal bets] may be long enough to stretch into the next administration," the law firm wrote (6) in an essay. "With many laws on the books and the potential for live claims under a future administration, companies should consider revisiting their policies and procedures that address insider trading to take into account prediction markets and new and emerging trading/betting platforms."
Article Sources
We rely only on vetted sources and credible third-party reporting. For details, see our ethics and guidelines.
ACI World (1); The New York Times (2); NPR (3); U.S. Department of Justice (4),(5); King & Spalding (6)
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Chris Morris is a veteran journalist with more than 35 years of experience, the majority of which were spent with some of the Internet’s biggest sites, including CNNMoney.com, where he was director of content development, and Yahoo! Finance, where he was managing editor. His work has also appeared on Fortune, Fast Company, Inc., CNBC.com, AARP, Nasdaq.com, and Voice of America, as well as dozens of other national publications.
