Why is Chicago called "The Windy City"?


“How should the songs of a windy city go?”

Carl Sandburg, The Windy City

Now this is a question that causes some debate in this area, and everyone is convinced that their viewpoint is right, whether they’ve researched the topic or not.

First, we’ll cover the origins of the moniker, then, since this is a paper intended to focus on weather forecasting issues, we’ll dig more specifically into the issues of wind in the Chicago area.

So let’s talk briefly about the myths.

Even a majority of Chicagoans I know hold to a nebulous belief that the “windy” part of the slogan has something to do with Chicago’s undeniably verbose political characters. There is a historical root to that belief, but some etymological researchers have discovered (when they dug deeply enough), that the phrase actually does simply promote Chicago as a breezy city.

Much of the myth dates back to Chicago’s attempt to land the World’s Fair (or “Columbian Exhibition”) of 1893. Chicago pulled out all the stops in their efforts to be named host, not unlike current efforts to be the host city of the 2016 summer Olympics. The city’s...persistence...led New York Sun Editor Charles Dana to write an editorial urging people to “ no attention to the nonsensical claims of that windy city”, and that it’s people could not hold a World’s Fair even if they won it. New York was also competing to host the Fair. Many consider this the origin of the phrase. The problem is, there are numerous references to Chicago as “the windy city” before Dana wrote his editorial.

We rely now on the research of expert amateur word-sleuth (and consultant to the Oxford-English Dictionary) Barry Popick. As it turns out, he has documented references dating back to the 1870's.

The phrase may have been generated by the Chicago Tribune in an effort to promote Chicago as a tourist destination. The phrase was used in the 1880's as a promotion of the refreshing lake breezes of “...the great summer resort of the west”. Previous to the 1880's, Chicago had been primarily known as “the Garden City”, with its latin motto: Urbs in Horto, or “City in a Garden”. So the slogan seems to be meteorological in origin, not political.

Now let’s look at Chicago’s location, and its north-south orientation along the shore of Lake Michigan.

Lake Michigan ranks as the fifth largest lake in the world, with a surface area of over 22,000 square miles, and an average depth of 279 feet.

It is Chicago’s proximity to this body of water that is probably its most interesting forecasting trip-up, and has the most impact on its winds.

How windy is the windy city? Actually, with an average yearly wind speed of about 10 miles per hour, Chicago fails to rank in the top ten windiest cities even in the United States, never mind the world (although Illinois as a state ranks about 5th in frequency of tornadoes). Mt. Washington, New Hampshire might deserve the slogan more than Chicago, with an average wind speed of 35 miles per hour in a kite-flying paradise.

However, Chicago does have a certain skyscraper fetish. With many of the tallest buildings in the world crowded into the downtown “loop” area just off the lake, a gusty funneling effect can create winds that will nearly knock the average pedestrian over. That effect is perhaps one of the leading causes of umbrella blow-outs in the world (admittedly, I haven’t done a lot of research on that) when Chicago has a decent storm. Plus, the buildings mean that the wind can be at your back walking down one block, then coming at you from the right on the next block, and from who-knows where on the next...

But, back to the lake. The lake breeze is created by a thermal gradient between a body of water and land, created by temperature variations caused by differences in solar heating between night and day.

The high specific heat of water means it doesn’t heat up as much as land, given the same amount of incoming solar radiation. So, during the day, land heats up more, and during the night, land cools off more.

The greater heating of the land creates rising air, and the lesser heating of the water can lead to sinking air. The rising air on land needs to be replaced, so a breeze blows in off the lake during the day.

At night, the land cools more than the lake, so rising air is usually found over the water, and the winds tend to blow from the land to the lake. The strongest lake breezed tend to occur during the late spring, when the water is still cold and the land is heating up nicely during the daytime.

The effect can be negated during the winter, when lake waters are warmer than the land all day and night, most notably when there is snow on the ground. Another wind effect that seems to receive little consideration in the Chicago area is the country breeze.

As defined by “The Atmosphere, 9th ed.” by Lutgens and Tarbuck, a country breeze is the result of heat accumulated by large buildings which tend to retain heat more than less built-up outlying areas. “The result is that the warm, less dense air over the city rises, which in turn initiates the country-to-city flow.” More to consider: Chicago’s combination of steel and concrete skyscrapers, asphalt roads and parking lots, and black-topped or shingled neighborhood roofs create a strong urban heat island tendency.

How do these factors combine?

The city of Chicago is located at 41 degrees of latitude, which places it (when considering the global circulation) in the heart of the westerlies, and frequently directly under the polar jet during the winter.

Those westerlies will be enhanced by the country breeze blowing in from the suburbs (re: the west) during the day, but counter-acted by the lake breeze blowing on- shore from the east.

The opposite effect happens at night, after the city buildings dissipate most of their retained heat. Then, the westerlies are backed up by the lake breeze blowing off- shore, and the country breeze, slowly becomes a non-factor.

The factors that should be taken into consideration when trying to forecast wind speed and direction in the Chicago area include the westerlies, the jet-stream, the lake breeze, the country breeze, and the urban heat-island effect. And even all that ignores any strong low-pressure systems moving into the area to create counter- clockwise flow.

All combined, these factors can make wind prediction difficult in the mid and upper levels of the atmosphere, and nearly impossible at ground level.

Of those elements, the one most-forecastable (I know, not really a word) seems to be the lake breeze effect. Forecasters will need to keep one eye on lake temperatures when figuring upcoming wind speeds/directions. The greater the difference between the lake temperature and the maximum heating of the land during the afternoon, the greater the strength of the lake breeze. Why does it matter?

The lake breeze effect isn’t limited to just wind. Air coming in from the lake also carries moisture with it. Moist air is less dense than dry air, which creates something of a feedback loop with the already-rising air over the land.

This can have one of several kinds of impact. Air flowing in from the lake can feed into the updraft region of a storm coming in from the west. The air coming in from the lake has a cooling effect in the summer, and a warming effect during the winter, creating complications when forecasting temperatures near the lakefront in almost any season. The lake breeze can also create a local-scale cold front, called the lake-breeze front.

The lake-breeze front is a narrow zone between the cooler temps near the lake and warmer inland temps, which can often literally be felt by a person passing through it. When the conditions are right, cumulus clouds can form and thunderstorms can pop up along this small boundary.

So forecasting for wind in the windy city isn’t just about forecasting wind. The jigsaw-puzzle like factors that come together to form wind vectors and strengths impact temperatures, humidity, precipitation, and even thunderstorms.

One has to keep in mind lake temperatures, incoming solar radiation, and the north-south wind component of high and low pressure systems coming in from the west, which can enhance or detract from what should be a relatively uncomplicated lake breeze in the windy city, this “great summer resort of the west”.

Something occurs to me...given that the Chicago culinary experience consists largely of items like Chicago-style hot dogs, Italian beef sandwiches, deep dish don’t think “windy” could be a gastro-intestinal reference... Forget I said anything.