Paris Weather Betting Probe Raises Integrity Concerns

French authorities have launched an investigation into possible manipulation of temperature data in Paris after a series of highly accurate bets generated substantial winnings on a prediction market platform.

The probe focuses on readings from a Météo-France weather station located at Charles de Gaulle Airport. These data points were used to settle wagers on Polymarket, where users place bets on real-world outcomes such as daily temperatures.

Suspicion arose following unusual betting activity in April, when large sums were placed on specific temperature outcomes. On 15 April, multiple participants predicted that the temperature would reach 19°C. Later that evening, the official reading rose sharply to match that exact figure.

Several accounts reportedly secured significant profits from the outcome, with three wallets earning a combined total of over $280,000. In a separate case, a single bet placed shortly before a late spike resulted in a gain of around $21,000. While each instance could be attributed to coincidence, the pattern has prompted closer scrutiny.

Météo-France stated that it detected irregularities both in the recorded data and in the condition of one of its instruments, leading to a formal complaint. The case is now being handled by France’s cybercrime unit. Authorities have not confirmed whether the equipment was tampered with or what may have caused the anomalies.

In response, Polymarket has stopped using data from the Charles de Gaulle station for its Paris-based markets and has switched to an alternative source at Paris-Le Bourget Airport. However, the platform has not voided bets settled using the disputed readings.

The situation highlights a broader challenge for prediction markets, which rely on external data sources to determine outcomes. While these systems typically function without issue, any potential vulnerability in data collection can raise concerns about reliability and fairness.

The investigation is ongoing, with authorities seeking to establish whether the temperature readings were legitimate or influenced by external factors. The case underscores the complexities involved when real-world data is directly tied to financial outcomes in digital betting environments.