French authorities opened an investigation this week after suspicious temperature spikes at a weather station near Charles de Gaulle Airport in Paris were allegedly used to manipulate betting markets on Polymarket, a prediction platform where users wager on real-world events. French media reports said the unusual readings helped traders make more than $35,000 in profits.

According to reports, the suspicious incidents occurred on April 6 and April 15, when temperatures recorded at the airport station suddenly jumped by several degrees within minutes despite surrounding weather conditions remaining stable. The abrupt spikes reportedly caused long-shot temperature bets on Polymarket to suddenly become winning positions worth thousands of dollars.

Investigators suspect the readings may have been artificially altered using a portable heat source, possibly a hair dryer, although authorities have not officially confirmed the exact method used. France’s national weather agency, Météo-France, said it detected both unusual sensor data and “physical observations” on one of its instruments before filing a criminal complaint.

The agency said the case involves possible interference with an automated data-processing system. No arrests or suspects have been announced. Meteorologist Ruben Hallali, who said he first flagged the anomalies, stated that the readings appeared inconsistent with nearby stations and broader weather conditions in Paris.

Following the incident, reports said Polymarket changed the weather station used for its Paris temperature markets. The case has drawn wider attention inside both financial and crypto circles over the vulnerability of prediction markets that rely on physical real-world data sources to settle bets.