Small wagers on Paris weather have turned into a big headache for both forecasters and a betting platform. An anonymous user on Polymarket turned a $119 punt into more than $21,000 after an April 15 contract tied to temperatures at Charles de Gaulle Airport suddenly swung in their favor late at night, Business Insider reports. The trader had bet that 18 degrees Celsius, around 64 degrees Fahrenheit, wouldn't be the day's maximum temperature, even though the market put that outcome at better than 90% odds. Around 9pm, the airport's reported temperature abruptly jumped from roughly 16 to 22 degrees, then fell back again. Nearby weather stations didn't record a similar spike.
Earlier in April, a Polymarket user made $14,000 in a similar longshot bet after another unusual rise in temperature readings from the airport's monitoring system, the Wall Street Journal reports.The odd spikes are now being investigated. Local weather enthusiasts contacted France's national weather service, Météo France, which filed a police complaint over suspected interference with its automated data system. The Guardian reports that Polymarket now relies on readings from the Paris-Le Bourget airport instead of Charles de Gaulle, but it hasn't refunded any bets.
The case adds a new twist to long-running concerns about insider trading on prediction markets, which already face scrutiny over bets linked to government actions and elections, Business Insider reports. Another platform, Kalshi, said Wednesday that it fined and suspended three US congressional candidates who wagered on their own races.
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