French police are investigating claims that a temperature sensor at Paris’s Charles de Gaulle airport was tampered with to win bets on Polymarket, after readings spiked unusually on 6 and 15 April, coinciding with large wagers on unusually warm weather.
The anomalies saw temperatures jump to 21C at 7pm on 6 April and 22C at 9:30pm on 15 April — figures that, according to Météo-France, had only a one percent chance of occurring on those dates. One trader won $21,000 (£15,600) on the latter date, contributing to a total of $34,000 (£25,100) in winnings tied to the suspect readings.
Polymarket, the world’s largest prediction market, had been using the Charles de Gaulle station’s data to settle bets on Paris temperatures for March and early April, with over $500,000 (£371,000) in play on some days. After the spikes, the platform switched to a sensor at Paris-Le Bourget airport but did not cancel contracts or refund bets.
French authorities confirm physical evidence prompted the investigation
Météo-France filed a complaint after identifying “physical findings on one of our instruments and the analysis of sensor data,” according to a spokesperson cited by both The Guardian and The Independent. The cybercrime division of the French police is now investigating the alleged tampering of an automated data processing system.
Sébastien Brana of the Infoclimat Association suggested the aberrant readings might have stemmed from operate done on the station’s shelter, initially suspecting sensor drift or maintenance issues — though Météo-France’s complaint points to deliberate interference.
Online bettors joked about hairdryers while stakes grew
On Polymarket’s Discord channels, users shared an AI-generated image of a man aiming a hairdryer at a weather station near a runway, with one asking: “What did you do to the temperature sensor at Paris airport yesterday? Was your weapon of choice a hairdryer or a lighter?” The post underscores the mix of irony and suspicion surrounding the incident.
The Independent notes that crypto outlets and trader publications floated the hairdryer theory, with weather forums speculating per Le Monde that a battery-powered device could have been used — though these claims remain unverified by investigators.
Prediction markets blur lines between information and influence
The episode highlights growing unease over platforms like Polymarket, which counts backers including a venture capital firm linked to Donald Trump Jr, and is increasingly used by traders and institutions such as Goldman Sachs to inform real-world decisions.
As The Guardian reported, bettors have previously threatened an Israeli journalist over a nearly $1m wager on whether Iran would strike Israel, and have discussed contacting the Institute for the Study of War to influence bets on Ukraine’s frontlines — despite those institutions having no control over how their data is used.
Could the temperature spikes have been caused by something other than tampering?
Météo-France initially considered sensor drift or maintenance work, and Sébastien Brana of Infoclimat suggested shelter repairs might explain the anomalies — but the agency’s formal complaint cites physical evidence and data analysis indicating deliberate interference.
Are bets placed on Polymarket still valid if the data source is later found unreliable?
Polymarket has stopped using the Charles de Gaulle sensor and switched to Paris-Le Bourget, but has not voided past bets or offered refunds, leaving the status of winnings tied to the disputed period unresolved.
