Polymarket Faces Questions Over $37K Paris Weather Wins

Brief temperature spikes determined the market outcomes, with one market settling after readings rose above 21°C and another after a jump from 18°C to 22°C. Blockchain analytics firm Bubblemaps said one trader earned more than $21,000 after buying NO shares on the 18°C outcome shortly before the second spike. 

Temperature Bets Raise Manipulation Fears

Two Polymarket accounts are facing scrutiny after reportedly earning around $37,000 from prediction markets tied to temperature readings in Paris. Questions are now being raised about whether the results were influenced by suspicious spikes in official weather data.

The controversy centers on contracts that used the highest temperature recorded at the Charles de Gaulle Airport weather station on April 6 and April 15. On both days, the final market outcomes appear to have depended on sudden and short-lived increases in temperature readings that quickly dropped afterward. These unusual fluctuations led analysts to question whether the readings reflected genuine weather conditions or possible interference.

According to French media outlet BFMTV, the station briefly moved above 21 degrees Celsius on April 6 before falling again soon after. That temporary rise was enough to determine the outcome of one prediction market, allowing the winning side to collect more than $16,000 in profits.

(Source: BFMTV)

A second incident on April 15 attracted even more attention. Blockchain analytics firm Bubblemaps reported that the station stayed near 18 degrees Celsius for most of the day before suddenly jumping to 22 degrees Celsius, only to decline again shortly afterward. Because the contracts were based on the day’s highest recorded temperature, the brief spike proved decisive in settling the market.

Bubblemaps also claimed that one trader purchased NO shares on the “18°C” outcome shortly before the sudden jump occurred. That trader later exited the position with profits of more than $21,000. The timing of the trade, combined with the rapid temperature increase, quickly intensified speculation about whether the market may have been manipulated.

More concerns were raised when analysts noticed that nearby weather stations did not record similar spikes at the same time. This discrepancy added weight to suspicions that the readings at Charles de Gaulle Airport may not have resulted from natural weather patterns.

Meteorologist Ruben Hallali told BFMTV that such abrupt changes in temperature over a very short period appeared highly unusual. He said the fluctuations were difficult to explain through normal atmospheric conditions alone. Hallali suggested it was possible that someone familiar with how the sensors operated may have interfered with the system, causing the temperature to rise just enough to influence the betting markets.

In response to the allegations, Météo France, the country’s official weather agency, reportedly filed a complaint with the Roissy Air Transport Gendarmerie Brigade. The complaint concerns suspected tampering with automated data systems connected to the weather station.