Météo France Files Police Complaint Over $35K Polymarket Weather Bet Anomalies

Polymarket traders won more than $35,000 after temperature sensor spikes near Paris-Charles de Gaulle airport resolved long-shot weather bets in their favor, prompting France’s national weather agency to file a police complaint. The incidents occurred on April 6 and April 15, when a Météo France sensor recorded temperature spikes exceeding three degrees Celsius before returning to normal within minutes, according to French broadcaster BFMTV.

Specific Trades and Payouts

On April 6, one trader earned $14,000 on a market linked to the sensor with an initial stake of only a few dozen dollars, BFMTV reported. A second trade on April 15 drew particular scrutiny from blockchain analytics platform Bubblemaps, which flagged an account that purchased “NO” shares on an 18°C outcome at odds below 1%, spent approximately $120, and exited with around $21,000—a 180x return—within 30 minutes of the spike.

Bubblemaps noted in a Wednesday post that this trade stood out from the account’s typical activity: “His average bet: $6 at 72% odds. This one: $120, 20x larger, at 0.6% odds — placed minutes before the anomaly.” According to BFMTV, the account that placed the April 6 winning bet had been created just two days before the trade, raising questions about potential market manipulation.

Météo France Police Complaint

Météo France filed a complaint with the Roissy Air Transport Gendarmerie Brigade for “interference with the operation of an automated data processing system,” according to a spokesperson for the weather agency. The agency cited “physical findings on one of our instruments and the analysis of sensor data” as the basis for the complaint.

Structural Vulnerabilities in Prediction Markets

Mark Roulston, a researcher focused on prediction markets at Lancaster University, told Decrypt that the incident exposes a fundamental weakness in how prediction markets are structured. “Basing a contract on the observations of a single weather station probably isn’t a good idea,” Roulston said. “Even in the absence of malicious activity, individual weather stations can develop faults or return anomalous readings.”

Roulston noted that national weather centres employ “procedures for weeding out anomalous readings” when using station data in their models. He suggested that basing contracts on an average across multiple stations would make them “less easy to manipulate” and “potentially more useful” for forecasting applications such as energy demand.

Broader Regulatory Context

The Météo France incident is the second market-integrity issue to affect Polymarket in as many weeks. Last week, UFC announcer Bruce Buffer misread a fight result live on air at UFC 327 in Miami, briefly sending one fighter’s odds to 99.9% before correction, enabling a trader to convert $500 into more than $252,000.

Prediction market platforms including Polymarket and Kalshi face mounting scrutiny. Last month, bipartisan U.S. senators Adam Schiff (D-CA) and John Curtis (R-UT) introduced a bill that would ban platforms like Polymarket and Kalshi from offering sports-related wagers altogether. Meanwhile, the Trump administration has filed lawsuits against Illinois, Arizona, and Connecticut, asserting that the CFTC has exclusive jurisdiction over the sector, following state actions against the platforms.

Polymarket is currently in talks to raise $400 million at a roughly $15 billion valuation, following a $600 million investment from Intercontinental Exchange last month.