French police are investigating suspicions that a hairdryer may have been used to tamper with official temperature readings, to make thousands of dollars on prediction markets. Readings at Paris’s Charles de Gaulle Airport unexpectedly spiked twice in the past month, reaching levels much higher than expected. Both times, gamblers on Polymarket, the world’s biggest prediction market, made large sums by betting on unlikely weather patterns. Météo-France, the weather agency, complained to police after readings twice unexpectedly reached 21°C.