Polymarket Traders Profit from Suspicious Paris Weather Data Spikes; Météo-France Investigates Possible Tampering

Was it a fluke of nature or market manipulation? France’s national weather agency, Météo-France, is now investigating after filing a complaint with local authorities over allegations that its Paris weather data was tampered with.

On April 6 and April 15, recording devices at Charles de Gaulle Airport detected dramatic, short-lived spikes in evening temperatures. The rapid rise and fall of temperatures raised suspicions at Météo-France, which suspects foul play.

“Based on physical findings regarding one of our instruments and an analysis of sensor data, Météo-France has indeed filed a complaint with the Roissy Air Transport Gendarmerie Brigade regarding the tampering with an automated data processing system,” the agency confirmed to DL News.

Polymarket Traders Win Big on Suspicious Weather Bets

A handful of new Polymarket accounts placed highly profitable bets on Paris weather during the two days in question:

• User Hoaqin won nearly $14,000 by betting $735 that Paris would reach 21°C on April 6. The same account also earned an additional $2,200 by betting that the highest temperature would not hit 18°C that day. The account was created less than 30 days prior.
• User Jiuzhou turned $500 into over $3,000 by betting that Paris would hit 22°C on April 15.

Meteorologists Question the Anomaly’s Nature

Ruben Hallali, a meteorologist and CEO of Sereno—a company that certifies weather data for insurance policies—highlighted the unusual pattern of the temperature spikes.

“What makes the Charles de Gaulle readings so striking is not just the magnitude of the spike, but its signature: a sharp, isolated jump at a single station in the early evening, absent from every neighbouring observation,”

Hallali told DL News. He added:

“In 15 years of operational meteorology, that is not something weather does on its own.”

Hallali also noted that the anomaly occurred precisely within the settlement window of a financial bet, raising further questions.

Polymarket Faces Past Manipulation Allegations

This is not the first time Polymarket, one of the world’s most popular prediction markets, has been scrutinized for potential manipulation. Digital investigators have flagged unusual trading patterns in specific markets:

• Just hours before US special forces captured Venezuelan President Nicolás Maduro in January, a newly created Polymarket account placed a $30,000+ bet on his ouster. The account’s total payout exceeded $436,000, sparking concerns of insider knowledge.
• US lawmakers have since introduced draft bills to regulate such platforms as they grow in influence.

Could a Hair Dryer Explain the Data Spike?

Some speculate that the Paris weather station data may have been deliberately interfered with—possibly using a hair dryer. Hallali suggested this is plausible:

“Weather stations are designed to measure the atmosphere, not to resist deliberate interference. A portable heat source held near the sensor housing for a few minutes is enough to raise the recorded temperature by several degrees without leaving any obvious trace.”

Polymarket has not yet responded to requests for comment.

Liam Kelly is DL News’ Berlin correspondent. Contact him at [email protected].