Polymarket trader bags $37K after sudden Paris temperature spike, probe begins- Moneycontrol.com

Météo-France filed complaint over suspected sensor tampering

Unusual temperature spikes at a key weather station in Paris have triggered an investigation after traders on Polymarket made about $37,000 betting on unlikely outcomes.

The bets were tied to daily temperature prediction markets based on readings from a Météo-France station at Charles de Gaulle Airport.

Data from the station showed sudden and short-lived spikes on April 6 and April 15, which determined the settlement of the contracts.

On April 6, temperatures briefly crossed 21°C before quickly dropping, while on April 15, readings jumped to around 22°C after hovering near 18°C for most of the day.

According to Bloomberg, these spikes represented the highest recorded temperatures for those days, allowing certain bets to pay out.

Market data cited in the reports showed that one trader made over $16,000 from the April 6 contract, while another gained more than $21,000 on April 15 by betting against the expected temperature outcome.

Blockchain analytics platform Bubblemaps flagged suspicious trading activity, noting that a trader began placing bets shortly before the spike occurred.

Meteorologists and analysts have questioned whether the readings could have been manipulated. Ruben Hallali, a meteorologist and CEO of weather intelligence firm HD Rain, told Bloomberg the sudden temperature changes were "very unlikely" to be natural and pointed to possible on-site interference with the sensor.

Following the anomalies, Météo-France said it had inspected the station and filed a complaint with airport police over suspected tampering with an automated data processing system.

The readings are not only used for forecasting but are also critical for aviation operations, including takeoff and landing calculations.

The incident has also raised broader concerns about the integrity of prediction markets, which have seen a surge in popularity.

Critics argue that such platforms are vulnerable to manipulation, insider trading, and regulatory gaps, especially when contracts depend on a single data source.

After the incident, Polymarket switched its Paris temperature data source to another airport station, according to its website.