Despite holding the title of ‘The Windy City’ Chicago is not particularly windy. Among major American cities, Boston, New York, Dallas, and San Francisco all experience stronger winds.
In fact, Chicago can’t even claim to have the strongest winds in the state; Springfield, Illinois, experiences annual winds that are, on average, half a mile per hour stronger than those in Chicago.
So why is Chicago the windy city? One reason, of course, is that in the 19th century, when the nickname was first used, Americans did not have lots of data on weather patterns that they could consult to crown Boston or San Francisco as the country’s windiest city.
The other, however, is that the name “windy city” seems to have been meant as much as an insult as an actual description of the weather.
According to many guidebooks and local institutions, the nickname reflects the long-windedness of Chicago politicians and the attendees of its many political conventions, as well as locals’ and politicians’ tendency to overstate the merits of their fair city. “During the mid-1800s nearly any city could (and did) proclaim itself the ascendant ‘Metropolis of the West,’" writes the Encyclopedia of Chicago.
Boosters of Chicago touted the city as they “sought to secure investment, workers, and participation in projects of national scope such as the building of railroads.” The Chicago Public Library adds, “Detractors claimed they were full of wind.“
From Alex Mayyasi's article 'Chicago Is Not The Windy City'