Traders are always trying to maximize their profits, and some bad actors even engage in illegal practices.
But one trader went a step further and manipulated the weather sensor in Paris with hair dryers to artificially spike temperature and pocket prediction wins worth $34,000.
Here is what happened.
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Météo France, the official French meteorological administration, filed a complaint with the air transport gendarmerie in Roissy for tampering with an automated weather sensor system at Paris Charles de Gaulle Airport, BFM reported on Apr. 20.
The meteorological administration decided to lodge a complaint because it recognized an unusual spike in temperature on two days this month.
On Apr. 6, the sensor reflected a spike of 4° C within 12 minutes at 6:30 p.m. It led to the temperature rising to 22.5° C before it returned to the normal level.
A similar incident occurred on Apr. 15 when the sensor recorded a spike to 22° C at 9:30 p.m. for a few minutes before returning to the normal level.
Meteorologist Paul Marquis said the pattern is hard to explain. A physical intervention with a heating device placed near the sensor probe was the most plausible explanation, he argued.
Interestingly, traders on the crypto-based prediction market, Polymarket, use weather sensor data at the Charles de Gaulle Airport to resolve the city’s temperature markets.
Launched in 2020, Polymarket is the world’s largest prediction market. It lets traders predict events like future Bitcoin price, weather, election results, government shutdown, etc., by paying with cryptocurrency.
Let’s look at the temperature markets on Polymarket on the two days.
On Apr. 6, a market on the highest temperature hitting 21° C paid out $14,000 to at least one Polymarket trader. This account was created only days earlier, as per the BFM report.
On Apr. 15, another market on the highest temperature hitting 22° C paid out $20,000 to the Polymarket trader.
So, this trader betting on Paris temperatures made roughly $34,000 on these two days when the Météo France suspects its sensor at the airport was tampered with.
On Apr. 19, Polymarket changed its reference sensor for validating Paris temperature markets from the Charles de Gaulle Airport to the Le Bourget Airport, BFM reported.
Location change for Paris temperature market on Polymarket
One X user suspected that the trader possibly used a hair dryer to spike the temperature at the sensor.
Podcast host Aakash Gupta opined that merely changing the location doesn’t change anything as the weather market on Polymarket is still open to similar manipulation.
The problem, he said, is that Polymarket relies on a single statistics provider, whether it’s weather or election market.
Related: NYSE owner acquires major stake in Polymarket
This story was originally published by TheStreet on Apr 23, 2026, where it first appeared in the MARKETS section. Add TheStreet as a Preferred Source by clicking here.