I recently came across a shocking case of prediction market manipulation, where someone actually used a hairdryer to make money. It’s a bit speechless. According to a report by The World Journal, a group of speculators near Paris Charles de Gaulle Airport blew air onto weather sensors with hairdryers, artificially raising the temperature, and then made a big profit on the temperature prediction market on Polymarket.

This happened from early to mid-April, and a few traders made over $35,000. The most outrageous case involved an account that only invested $120, yet in just 30 minutes, earned more than $21,000, with a return rate soaring to 180 times. Blockchain analysis platform Bubblemaps found that just minutes before abnormal temperature data appeared, someone suddenly heavily bet that the day’s high temperature would exceed 18°C. At that time, no one expected this outcome, with less than a 1% chance of winning. After the sensor was artificially influenced and the temperature spiked, this trader won outright.

The dramatic part is that the French meteorological agency later discovered the sensor was tampered with, and the temperature rose over 3 degrees Celsius within a few minutes before quickly returning to normal. This isn’t just a market manipulation issue; the meteorological agency also filed criminal charges with the French Air Transport Gendarmerie because such human interference affects data accuracy and threatens safety decisions in the aviation industry. French police are now investigating.

This incident exposed a critical weakness in Polymarket. The entire Paris climate market’s settlement relies entirely on a single official data source from the French meteorological agency, making it especially vulnerable to physical manipulation. Mark Roulston, a researcher at Lancaster University studying prediction markets, pointed out that relying solely on a single weather station’s readings for high-stakes contracts is too risky. He recommends future prediction contracts should be based on the average of multiple sensors to reduce single-point failures and manipulation risks.

Ethereum co-founder Vitalik Buterin also commented on this, noting that similar issues have appeared before in military intelligence prediction markets. Vitalik emphasized that to maintain integrity, prediction markets should enforce median settlement mechanisms based on multiple independent sources, rather than relying on a single, easily manipulated data source. He also suggested platforms develop more conditional markets to evaluate the relationship between specific decisions and outcomes.

Interestingly, this event occurred while prediction markets are facing regulatory challenges worldwide. The U.S. has proposed banning sports prediction markets to preserve event integrity. Polymarket is restricted in France due to gambling license issues, but in the U.S., it has gained some policy support. However, the hairdryer incident at Charles de Gaulle Airport serves as a reminder to the industry that ensuring the authenticity of underlying data is the core challenge for mainstream adoption of prediction markets.

Ironically, despite ongoing controversies, Polymarket’s capital continues to grow. The platform is seeking a new $400 million funding round, with a valuation of $15 billion. Intercontinental Exchange recently invested $600 million, indicating that traditional financial institutions remain very interested in these new data trading tools. The Charles de Gaulle hairdryer case essentially warns the market that improving data verification mechanisms may be the key to whether prediction markets can truly mature.