Polymarket traders win $37K after Paris weather data glitch, raising suspicion

Two Polymarket accounts have attracted suspicion after making $37,000 betting correctly on two unusual temperature readings of a weather station located in a major airport in France.

The two weather-focused prediction markets focused on the highest temperature in Paris on April 6 and 15, using the highest temperature recorded at the Charles de Gaulle Airport Station in degrees Celsius, according to Polymarket.

French media outlet BFMTV reported on Monday that the temperature suddenly climbed to over 21 degrees Celsius on April 6, before dropping again immediately. The market resolved with the winner taking over $16,000. The winning account is under 30 days old.

Meanwhile, blockchain analytics tool Bubblemaps reported a similar glitch for the April 15 market. The weather station showed 18 degrees Celsius most of the day, then suddenly spiked to 22 degrees Celsius before dropping back.

Some have questioned whether foul play was involved. Prediction markets are already facing growing scrutiny over insider trading and possible violations of gambling laws.

“That spike didn't show on nearby stations,” Bubblemaps analysts said, adding that “Just before the spike, one trader started buying NO shares on 18°C,” before exiting with over $21,000.

The winning trader account has been highly active on Polymarket with wagers on crypto and weather. However, this is the largest payout by a wide margin; the next-highest is $13.

Ruben Hallali, a meteorologist, told BFMTV the temperature glitch was unlikely to be a natural event and alleged it may have been tampered with on-site.

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“Such temperature variations seem very unlikely, especially on these two dates, and over such a short period. We can imagine that an individual with a good understanding of how the sensors work intervened, resulting in temperatures rising by two degrees at the right time, to validate a bet,” he added.

Météo France, the official government weather agency of France, has reportedly made a complaint with the police unit the Roissy Air Transport Gendarmerie Brigade, for alleged tampering with the operation of its automated data processing systems.

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