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Two Polymarket accounts came under scrutiny after Paris temperature markets reportedly paid them about $37,000 from contracts tied to official weather readings. The markets used the highest temperature recorded at Charles de Gaulle Airport on April 6 and April 15. On both days, short spikes settled the outcomes and triggered questions about possible interference with the data. French media, analysts, and meteorologists all focused on readings that rose sharply and then fell soon after.
BFMTV reported that the temperature briefly rose above 21 degrees Celsius on April 6 before dropping again. That short move settled one market and let the winning side collect more than $16,000. Then, on April 15, the temperature stayed near 18 degrees for most of the day before jumping to 22 degrees. The reading soon fell, yet the day’s high had already fixed the result.
Analysts then noted that nearby weather stations did not record matching spikes at the same times. Meteorologist Ruben Hallali told BFMTV that such abrupt changes looked highly unusual over a short period. He said normal atmospheric conditions alone did not easily explain the swings. He also said someone familiar with the sensors may have pushed temperatures just high enough to affect the bets.
Bubblemaps added another layer to the dispute with a trading timeline of the April 15 market. The firm said one trader bought NO shares on the 18°C outcome shortly before the sudden jump. That trader later closed the position with profits above $21,000.
French reporting also linked earlier wins to accounts that backed long-shot outcomes tied to the brief peaks. Le Monde and BFMTV said a bettor whose account appeared days earlier made about $14,000 on Paris reaching 21 degrees on April 6. A similar wager on 22 degrees then paid roughly $20,000 on April 15.
Together, both events produced about $34,000 in gains, based on the reported payouts. At the same time, Polymarket users flagged the activity in real time. Comments on the platform cited manipulation and insider trading as the spikes resolved the contracts.
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In response, Météo France reportedly filed a complaint with the Roissy Air Transport Gendarmerie Brigade. The complaint concerns suspected tampering with automated data systems linked to the weather station.
Paul Marquis, founder of E-Meteo Service, also said the pattern did not fit a natural explanation. “There was no change in wind direction or relative humidity, and the other stations recorded nothing,” he told Le Figaro. He said a heating device near the probe offered the most plausible explanation. The station sits near the runway perimeter and remains accessible from a public roadside area.
Polymarket uses that station to settle its Paris daily maximum temperature markets. The platform is banned in France, yet some people in the country can still access it. Around April 19, the platform switched Paris weather markets from Charles de Gaulle to Paris-Le Bourget Airport. That change ended further reliance on the compromised location.
Polymarket Paris weather bets came under scrutiny after brief temperature spikes at Charles de Gaulle Airport decided two contracts and reportedly delivered about $34,000 in gains. With Météo France filing a complaint and analysts questioning the data, the case has sharpened focus on how real-world inputs can affect prediction market outcomes.
