Anyone who's grown up in Illinois is familiar with tornadoes, as they are an unfortunate part of spring. The flowers may be blooming, and the temperature may be nice, but it's likely that you'll find Illinoisans retreating to basements during a storm.
Illinois is located in what is called Tornado Alley, the flat plains area of the country that is prone to tornadoes. They come with the territory when it comes to spring on the Great Plains.
How do tornadoes work?
A tornado is basically a violently spinning column of cloud that usually forms during an especially strong storm. By definition, it is only classified as a tornado when its top touches the cloud and its bottom touches the ground. If it does not touch the ground, it is called a funnel cloud, which is still quite dangerous. Sometimes tornadoes can be invisible, if no water or debris accumulates around their winds. The winds in a tornado cause an area of extreme low pressure, and this usually gathers condensed water from the cloud around it, as well as dust. This is what causes the tornado to be visible. However, it can go through clearer skies without accumulating much water, making a much more dangerous and less visible tornado. This would be classified as a tornado without a funnel cloud.
There are different classifications of tornado, and the National Weather Service uses something called the Fujita Scale to sort them all. The Fujita scale runs from least intense (F0) to most intense (F5). An F5 tornado is so strong that it can be up to a mile wide, and it can decimate entire towns because of this. An F0 tornado, in contrast, only causes light damage, and is usually quite a small tornado. F0 and F1 tornadoes are the most common types of tornado, which is lucky for us. The damage levels seem to increase exponentially as the tornado levels go up, so even if tornadoes are common here, they are usually relatively mild.
Why Illinois is so tornado-prone
One of the reasons scientists pose for why there are so many tornadoes in this area is the different combinations of air that come together here. Three sources of air meet in the Midwest: warm, humid air from the Gulf of Mexico; cold, dry air from Canada; and warm, dry air from the Southwest Desert. Reactions of such different areas of air are bound to be volatile, so they tend to produce strong storms. Since tornadoes tend to come from strong storms, it makes sense that the different combinations of air contribute to indirectly causing the frequency of tornadoes here.
Although incredibly dangerous, tornadoes are certainly interesting. It's very unwise to observe them in real time, but reading about them and watching videos can be fascinating. They can teach you both how tornadoes work, as well as precautions you should take in a tornado-heavy area.
Above all, stay safe!