Two Polymarket accounts came under suspicion after correctly placing $37,000 in bets on two unusual temperature readings at a weather station located at a major airport in France.
Two weather-focused forecast markets focused on the highest temperature in Paris on April 6 and 15, using the highest temperature recorded at the station at Charles de Gaulle Airport in degrees Celsius, Polymarket reports.
French media BFMTV reported on Monday that the temperature suddenly rose to over 21 degrees Celsius on April 6 and then immediately dropped again. The market was settled and the winner took over $16,000.
Meanwhile, blockchain analytics tool Bubblemaps reported similar error for the April 15 market. The weather station showed 18 degrees Celsius for most of the day, then suddenly rose to 22 degrees Celsius, then dropped.
Some question whether foul play occurred. Prediction markets are already facing increasing scrutiny over insider trading and possible violations of gambling regulations.
“This spike was not visible at nearby stations,” Bubblemaps analysts said, adding that “just before the spike, one trader started buying NO shares at ’18°C’ before Exit with over $21,000.
Meteorologist Ruben Hallali told BFMTV that the temperature difference is not a natural phenomenon and speculates that it may have been faked on site.
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“Such temperature fluctuations seem very unlikely, especially on these two dates and in such a miniature time. We can imagine that someone with a good understanding of the sensors intervened, causing the temperature to rise by two degrees at the right time to confirm the bet,” he added.
Météo France, France’s official government weather agency, has reportedly filed a complaint with its police unit, the Roissy Air Transport Gendarmerie Brigade, over alleged interference with its automatic data processing systems.
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