Two Polymarket accounts have raised suspicions after earning around $37,000 by correctly betting on unusual temperature spikes recorded at a weather station at a major French airport.
The bets were placed on two weather-based prediction markets tied to the highest temperature in Paris on April 6 and April 15, using readings from the Charles de Gaulle Airport station, according to Polymarket.
French outlet BFMTV reported that on April 6, the temperature briefly jumped above 21°C before quickly dropping back, allowing the winning position to claim more than $16,000.
A similar anomaly was flagged for the April 15 market, with blockchain analytics firm Bubblemaps noting that the temperature hovered around 18°C for most of the day before suddenly spiking to 22°C and then falling again.
The incidents have prompted speculation about potential foul play, as prediction markets continue to face increased scrutiny over insider trading risks and possible breaches of gambling regulations.
“That spike wasn’t observed at nearby stations,” Bubblemaps analysts said, noting that “just before the surge, one trader began buying NO shares on ‘18°C’ before exiting with more than $21,000 in profit.”
Meteorologist Ruben Hallali told BFMTV that such a fluctuation was unlikely to occur naturally. “Temperature swings like this are highly improbable, especially on those dates and within such a short timeframe. It’s possible that someone with knowledge of how the sensors operate interfered, causing a brief increase of a couple of degrees at a critical moment to validate a bet,” he said.
France’s national weather agency, Météo-France, has reportedly filed a complaint with the Roissy Air Transport Gendarmerie Brigade, alleging potential tampering with its automated data processing systems.
