At around 9 p.m. on April 15, 2026, a weather sensor at Paris Charles de Gaulle Airport suddenly jumped from 16°C to 22°C. 24 minutes later, the temperature quietly returned to its original reading.

During the same period, all surrounding weather stations showed no such change. The French Meteorological Office later conducted a physical inspection and data analysis of the sensor. After ruling out equipment failure, they discovered evidence of "human-induced tampering": someone had stealthily heated the sensor.

As of the time of this article's publication, the French Meteorological Office has officially filed a criminal complaint with the Roissy Airport Gendarmerie. If convicted, the perpetrator could face the highest penalty under French law for tampering with a public institution's automated data processing system: 7 years in prison and a €300,000 fine.

What seems like a minor and abstract incident actually points to a prediction market platform called Polymarket.

Prediction Market Principle

Polymarket is a blockchain-based binary options prediction market platform. Here, users can bet on any event with a clear outcome, from "Can Trump win the election" to "Will today's high temperature in Paris exceed 22°C."

Each market has only a "yes" or "no" answer, and the real-time price fluctuations precisely represent the likelihood of the event occurring, reflecting participants' collective judgment on the outcome. Correct guesses earn profits proportionally, while incorrect guesses result in a loss of the principal.

For markets such as the highest temperature in a region, Polymarket uses official data from specific weather stations as the settlement basis to avoid ambiguity. In the Paris daily high temperature market, the settlement source is the automated weather station at Paris Charles de Gaulle Airport (LFPG station).

The rules themselves are not the issue—until someone realized that this sensor was placed just outside the runway fence, near a public road, with almost no fencing or cameras around, making it accessible to anyone.

178x Gains in Half an Hour, Using Only a $35 Hairdryer

Around 9 p.m. local time in Paris on April 15, the probability on Polymarket for "April 15 Paris High Temperature is 18°C" had already exceeded 99%. At this point, as the temperature began to drop into the night, the market seemed to have entered the "garbage time."

However, at this moment, an account with the ID xX25Xx placed a hefty $120 bet on "No" — due to the probability equating to odds mechanism, the potential return behind this bet exceeded $20,000.

Nevertheless, traders at that time did not take this bet seriously. On this platform, the "go big or go home" gambler mentality is not uncommon, and standing against these gamblers to earn their stake back is actually one of the most stable ways to profit.

Following the subsequent temperature reading announcement, the sensor jumped from 16°C to 22°C. The probability of "highest temperature being 18°C" instantly dropped to zero. xX25Xx's initial $120 bet multiplied by about 178 times, causing significant losses for those professional traders and quant robots who had long been in such markets and had been consistently profitable.

Meteorologist Paul Marquis later pointed out: "With no changes in wind direction and relative humidity, no records at other stations, the most reasonable explanation is physical intervention using heating equipment near the sensor probe."

The motive behind tampering with the temperature data now became clear: with a deep understanding of weather sensor principles, xX25Xx first placed a high-odds bet that the day's highest temperature would exceed 18°C, then manipulated the sensor data by artificially heating the sensor to profit from it.

xX25Xx has since changed their account ID, seemingly deliberately avoiding public scrutiny; however, thanks to Polymarket's blockchain-based mechanism, all of their transaction records remain publicly accessible.

The Ultimate "Oracle" of Leading Polls

Polymarket doesn't just bet on the weather. Here, you can bet on whether Israel and Hamas will have a ceasefire, bet on whether the Fed will cut interest rates next time, bet on which profession will be replaced by AI next. Its markets cover politics, economics, technology, sports, natural disasters; almost any event with a clear outcome can become a trading target.

What truly brought the prediction market into the spotlight was the 2024 U.S. presidential election. At that time, most polls showed a close race between Trump and Harris, while the prediction market consistently gave Trump's election probability as over 90%. The end result proved that this real-money-driven "collective judgment" pointed to the correct answer earlier than the vast majority of professional polls.

Following this incident, the prediction market is increasingly seen by many as a unique information tool—not gambling, but a "real-money vote-based opinion poll." Participants stake real funds, so they have an incentive to gather genuine information rather than just provide a gut feeling answer. In theory, this mechanism should make market prices reflect the true probability more accurately.

However, this logic has a vulnerability: the greater the influence, the stronger the motivation to attack. When the prediction market becomes the global media's "oracle," when its price starts influencing people's judgment of real-world events, the vulnerability of every data source becomes an exploitable loophole.

The weather market happens to be one of the most vulnerable in this regard. And the ways to exploit these vulnerabilities go far beyond just tampering with a heating sensor.

An Airport Temperature Recorder Nobody Cares About Is Now Running a Paid Group

Aside from physical tampering, informational asymmetry itself is another widely discussed "advantage source" in the weather market.

This month, Polymarket launched daily high-temperature markets for several Chinese cities, including Shanghai Pudong Airport, Shenzhen Bao'an Airport, and Beijing, with settlements also relying on airport METAR data.

According to discussions in the trading community, a new type of "weather oracle" has emerged in these markets, different from professional traders and quantitative robots—they always manage to lock in a betting direction related to temperature changes before the weather data is publicly updated.

Unlike building prediction models using open-source weather data, these traders seem to have a significant time advantage. Rumors even circulate in the community about individuals sharing their profit screenshots and operating strategies publicly, as well as running paid groups.

In a weather market that was least likely to have "insiders," meteorological message delays and differences in data update frequencies are now causing traders to widely question the reliability of the weather markets in some Chinese cities.

When weather data becomes an asset that can be priced and traded, those who understand this data have transformed from being ignored to becoming the most valuable players. Those holding METAR data reading channels and being one step ahead of the market suddenly find themselves in an unexpectedly advantageous position.

Heating a Sensor for Half an Hour Moved the Trust Foundation of a Trillion-Dollar Business System

So far, this may sound like a financial game played within the prediction market niche. The bets were only a few thousand dollars, and the wins and losses circulated only within that circle.

However, the METAR data from airport weather stations has never been solely used for Polymarket's settlements.

Every operational decision of an airline is based on meteorological data. According to data from the FAA, over half of flight delays are weather-related, and extreme weather is the single largest cause of 42% of flight cancellations. Weather-related flight disruptions cost the aviation industry over $60 billion annually. Behind this number are numerous scheduling decisions that rely on accurate data.

The pricing logic of agricultural insurance is also built on meteorological data. The global agricultural insurance market is approximately $46 billion, with a large portion of products utilizing parametric insurance mechanisms—when meteorological indicators such as temperature and rainfall trigger preset conditions, payouts are automatically triggered without the need for manual assessment. The premise of this mechanism is reliable and truthful meteorological data. If the data is tampered with, the triggering conditions would be distorted.

One level above is reinsurance. Global reinsurance companies price their exposure to extreme weather events based on actuarial models built on long-term meteorological data. A data quality issue at one site may have limited impact in a single event; however, if such low-cost replication of manipulation targeting a single data source is proven to be possible, the credibility of climate data would be fundamentally undermined.

These are just the known and traceable commercial dependencies. Energy companies use meteorological data to forecast peak electricity demand; logistics companies use it to plan routes and warehouses; the construction window of building projects relies on weather forecasts; and the price fluctuations of commodities futures are based on real-time assessments of agricultural weather conditions.

In this system, the sensors of weather stations are the lowest-level input. To earn a few extra thousand dollars in a predictive market, someone placed a heating device near that sensor—a seemingly minor action, but one that touches upon a data chain extending from airport runways to the global financial market.

Currently, France is still investigating this incident. Following Polymarket's switch of settlement sources for the Paris market, no settled markets have been refunded. The profits from earlier accounts remain in place.

The potential risks behind this event may be higher than we imagine. The objectivity of temperature data makes it relatively easy to detect anomalous behavior, but in the realm of predictive markets, there are still many markets settling based on a single source of information—some of which involve events far more complex than weather and are much harder to independently verify.

Predictive markets were once called the "ultimate oracle" for revealing the truth. When their own data sources begin to be targeted, the implications of this title become much more complex.