The real-world consequences of gambling on the weather
Making bets on the weather is a practice that goes back centuries. In an age of climate change and online betting markets, the stakes are much higher.
On April 15, the recorded temperature at the Charles de Gaulle airport suddenly rose higher than anywhere else in Paris. An anonymous Polymarket user, who had wagered that the highest temperature in Paris that day would be 22 degrees Celsius, pocketed $21,398. When meteorologists determined that the temperature increase could not have occurred naturally, authorities began to investigate possible tampering with a French meteorological service device.
This potential sabotage is more than just another instance of the behavior incentivized by buzzy online prediction markets like Kalshi and Polymarket that let users bid on just about anything. The incident in Paris is also part of a longer history of gambling on the weather, a ubiquitous practice that has been hidden in plain sight, but is suddenly drawing attention now that anyone can place these bets on their phones.
Most users of online prediction markets bet on sports, political elections, and other topics for entertainment, but a small subset of users has gone all in, turning these platforms into full-time jobs, specializing in certain markets and using complex algorithmic tools to find the slightest advantage or opportunity for arbitrage, analyzing risk the way financial traders do. And although betting on the weather (and manipulating data to win) is not new, the stakes are much higher in our climate-changed world.
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Rain betting is a widespread tradition reaching back centuries. Part of its appeal was that, as one newspaper noted of monsoon betting in late 19th-century India, there was “no opportunity for cheating.” No one could make it rain, and everyone could see whether there was “a heavy shower or none at all.” People placed yes/no bets on binary events: whether or not a rain gauge or gutter would overflow, or whether a specific amount of precipitation would fall. As historian Ritu Birla has shown, before it was outlawed in the 1890s, “rain speculation” in Kolkata and Mumbai was both a form of community recreation and a mode of “vernacular capitalism” that strengthened the power of the Marwari business class.
Despite the rain gauge’s precision measurement, reports surfaced of attempted manipulation in which, as the New York Times reported in 1871, “villainous speculators sometimes try to make a corner by stopping up the pipes.”
In the 20th century, weather gambling became more organized and more data-driven in the United States. Powerful Chicago “Gambler Boss” Jim O’Leary, known as “the man who would bet on anything,” ran a well-known “weather book” in the early 20th century. Chicagoans came to O’Leary’s saloon and “gambling resort” to bet on horse racing, sports, and elections in addition to weather.
In 1908, there was a public dispute between O’Leary and the U.S. Weather Bureau over the exact number of rainy days in Chicago in May. O’Leary had bet big and won when rain came at the end of the month. He had guessed correctly at a time when government meteorologists insisted that making long-range forecasts was impossible. His victory further popularized betting on the weather (and, to the chagrin of scientists, seemed to imply that speculators like O’Leary knew as much, or maybe more, than they did). O’Leary’s winning bet simultaneously added weather to the list of things he could seemingly guess and undermined fragile public trust in government weather science. The New York Times reported, “Chicago takes O’Leary’s word on the weather. His latest victory has fixed his status as a weather prophet more firmly.”
Weather speculation only escalated from there, with betting on the daily temperature becoming a big business for gambling syndicates in major U.S. cities by the 1910s and 1920s. The syndicate in Albany made a reported $2,300 a day running a weather lottery based on temperature data for randomized cities, selling 20,000 tickets per day. Other “weather pools” involved wagering on what the temperature would be at a certain time the next day.
The government weather data published in daily newspapers was critical to these operations as the official standard used to determine winners. In St. Louis and other U.S. cities in the 1920s, “persons anxious to make a killing in the weather report gambling,” as the Maryland Midland Journal described them in 1929, offered government weather officials bribes of up to $1,000 to falsify the hourly temperature record printed in newspapers.
St. Louis also had to contend with gamblers who tampered with daily temperature data while messenger boys were carrying it to newspaper offices. In response, the Weather Bureau asked newspapers not to accept any government weather reports with erasures on them. There was even talk in New Orleans of newspapers suspending the publication of weather data for a month to curtail the gambling. After rumors in 1929 that the New Orleans weather official had stopped issuing hourly temperature reports, the Weather Bureau chief said, “‘Regardless of the gambling on these figures, we can’t very well withhold such important information from the public.’”
Gambling was mostly illegal in the United States by 1910, but anti-gambling laws were enforced inconsistently in the early to mid-20th century. O’Leary and the weather gambling syndicates operated in public view, yet regularly evaded prosecution, whether by concealing their activities or paying off the police. As horse racing and bingo were legalized between the 1930s and the 1950s, crackdowns on forms of still-illegal gambling increased.
In 1950, the St. Louis police captain testified before a Senate special committee on organized crime and included “weather tickets” alongside numbers, handbooks, and pinball machines in his list of widespread forms of gambling that law enforcement sought “to suppress . . . as near as possible.” At that point, the St. Louis “‘weather-betting’ racket” was reportedly raking in $2.6 million a year. By the early 1950s, Missouri had a law on the books outlawing “weather-ticket” lotteries.
As state lotteries became legal again and casinos opened in the late 20th century, weather gambling faded into the background. Quietly, it took different forms, from weather derivatives to online forecasting contests, throughout the late 20th and early 21st centuries. But in the past decade or so, as the worsening climate emergency continues to scramble what once seemed like predictable patterns, gambling on the weather has surged again—this time in the online betting markets that have proliferated as the planet has warmed. Tampering with an airport weather device, as allegedly happened in Paris, shows how online prediction markets can incentivize manipulation of not just a betting platform but also real-world conditions.
Furthermore, the more users who place bets on temperature, precipitation, and climate impacts, the more transaction fees are pocketed by the companies running these platforms. In this way, a climate-changed planet is good for business for online prediction markets.
As of this writing, Polymarket users have wagered $3 million on where 2026 will rank, temperature-wise, with 35 percent betting that it will be the hottest year on record and 56 percent betting that it will be the second-hottest. One commenter wrote, “go 2026.” Ironically or not, rooting for short-term personal financial gain over the long-term future of our planet is the new business model for weather gambling in the age of online prediction markets.
Jamie Pietruska is a historian at Rutgers University who is currently writing a book called Weather Capitalism: Gambling on the Weather from Rainfall Lotteries to Wildfire Markets.
Made by History takes readers beyond the headlines with articles written and edited by professional historians. Opinions expressed do not necessarily reflect the views of the Inquirer.