In France, Météo-France has reported a suspicious incident to the police, claiming that an unknown perpetrator allegedly manipulated the temperature readings at the Charles de Gaulle Airport weather station using a battery-operated hairdryer. This manipulation was aimed at influencing contracts related to temperature predictions on the Polymarket forecasting platform.
On April 6 at 18:30 and April 15 at 21:30, the temperature at the station spiked sharply by 4–6 degrees (reaching 22.5°C and 21.9°C respectively) before quickly dropping back to its original level. Players who purchased contracts betting on high temperatures during these intervals won $14,000 and $20,000 respectively.
The weather station is located near a public road. Initially, these spikes were attributed to a possible sensor defect or direct sunlight; however, the second spike occurred after sunset. Following these incidents, the forecasting platform implemented geo-blocks for users from France, where their activities were already illegal.