Météo-France, the national meteorological service, has opened an investigation into whether its weather sensors were deliberately compromised after unusual temperature readings coincided with large payouts on the blockchain-based prediction platform Polymarket. The inquiry focuses on a sensor located near the perimeter of Paris-Charles de Gaulle airport, which recorded a sharp 4°C rise in just twelve minutes on 6 April, crossing the 22°C threshold despite other nearby sensors showing significantly lower temperatures.
A user on Polymarket had placed aggressive bets on temperatures exceeding 21°C that day, even though the consensus forecast was around 18°C, and reportedly profited nearly €30,000. A second similar anomaly occurred on 19 April, further fueling suspicions of tampering. Online rumors, though unverified, suggest that a hair dryer may have been used to artificially heat the sensor.
Investigation and Response
Météo-France has filed a complaint with the Roissy air transport gendarmerie brigade for “alteration of the operation of an automated data processing system.” The agency stated that an analysis of sensor data revealed irregularities that prompted the legal action. Polymarket, which relies on a single Météo-France sensor at Charles de Gaulle to settle temperature bets for Paris, has since switched its resolution metric to the sensor at Paris-Le Bourget airport. However, the platform did not cancel the affected contracts or refund bets, leaving the resolved payouts final—a departure from previous instances where it suspended resolution pending clarification.
This incident has reignited debate over the reliability of “oracles” in decentralized finance. Oracles are mechanisms that feed real-world data into smart contracts to determine financial outcomes. Polymarket pulls data directly from official government websites, but if the primary source is corrupted, the platform lacks internal verification mechanisms. The decentralized nature of these platforms also makes it difficult to freeze assets, even if investigators identify the individuals behind suspicious trades.
The case underscores a growing frontier in white-collar crime, where physical-world manipulation targets automated prediction markets. As Europe grapples with the implications of decentralized technologies, this incident highlights vulnerabilities that could affect other sectors. For instance, the rapid obsolescence of drone technology similarly challenges regulatory frameworks, while the EU's lag in satellite defence illustrates broader gaps in technological oversight.
Polymarket’s decision to maintain the resolved contracts has drawn criticism, as it contrasts with its earlier caution in similar situations. The platform has previously suspended bets until rules and circumstances were clarified, but in this case, it opted for finality. This inconsistency raises questions about governance in decentralized markets, where transparency and accountability remain contentious issues.
The investigation by French authorities is ongoing, and no charges have been filed. However, the case serves as a cautionary tale for the growing intersection of physical infrastructure and digital finance. As Europe continues to integrate blockchain technologies, ensuring the integrity of data sources will be critical to maintaining trust in these systems.
